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CAMELOIPARDUS

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star atlas and telescopic handbook (ep

Cornell University

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the Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

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SKETCH MAP OF THE Moon
(as seen in an inverting Telescope).

A STAR ATLAS

AND TELESCOPIC HANDBOOK

(EPOCH 1920)

FOR STUDENTS AND AMATEURS

Covering the whole Star Sphere, and showing over 7000 Stars, Nebule,
and Clusters; with Short Descriptive Lists of Objects suitable
for Small Telescopes; Notes on Planets,
Star Nomenclature, ce.

BY

ARTHUR P. NORTON, B.A.

Taondon:
GALL AND INGLIS, 31 HENRIETTA STREET, STRAND, W.C.;

AND EDINBURGH.
1910
EM

eT

ASTOTSS

Astronomical Publications.

By WILLIAM PECK, F.R.A.S., F.R.S.E.

The Observer's Atlas of the Heavens
A magnificent Atlas containing 45 folio pages of Large
Scale Astronomical Charts, compiled Fam the latest
information, also Catalogues of Double Stars, Nebule,
Clusters, Variables, &c., &c. Size of each map 134 x9h.
Bound in Both, net, 21/-
(Prospectus on application.)
The. Constellations and How to Find Them
FoR NORTH. HEMISPHERE.—/ Gt. Britain, Pureeel

Canada, and U.S.) Clo 2/6
FOR SO. HEMISPHERE. —( Australia, N. Zealand
Cape Colony, &e.} . Clo 3/6

Each Book contains 14 Star ‘Maps, (6 inches diiacterh
with descriptions, showing Stars visible in each month.
For those ee telescopes.
Map of the Moon, showing names of over 350
raters, Seas, fees with Index: and desoriptlve letter-
press, .. * oe .. Paper Cover, 1/-

Norton’s Star Atlas and Telesene Handbook,
showing positions of practically all objects in Webd's’
Celestial Objects, and Smyth's Cycle or Celestial Ob-
Jects, for epoch 1¢20, and covering the star sphere.

16 charts, prepared with he very greatest care, with
letterpress. Demy dto, By A. P. Norton, B.A. net, 5/.

An Easy Guide to The’ Constellations
For countries north of the Equator. By Rev. J.
GALL. 30 Plates with descriptive letterpress. 267720.

Paper, 1/-. Cloth, 1/6

An Easy Guide to Southern Stars.

Uniform with the above volume for Northern Hemi-
sphere. By M. A. Orr (Mrs. John Evershed).
Cloth limp x/-, ae = lettered 1/6

The People’ s Atlas of The Sta
(for both N. Hemsph) Scamaenlen tothe Zasy
Guide. 6 lane ese Star Charts, 4 showing the Stars
in white on a dark blue ground. Qzavto,Paper Cover, 1/-

Gall & Inglis, 31 Henrietta Street, London: & Edinburgh.

PREFATORY NOTE

Tus Atlas is primarily intended for the use of those amateur telescopists whose instruments are mounted either
on alt-azimuth stands or as equatorials without graduated circles.

In order to make proper use of a set of star maps, however, it is necessary to be able to recognise at least
the more important constellations and their relative positions. It is also necessary to have a proper conception
of their apparent daily motions. There is a very useful little book, “An Easy Guide to the Constellations,” by
the Rev. James Gall (Gall & Inglis), which could be used by the beginner with great advantage as an introduction
to the present work.

Short popular explanations of various astronomical terms met with in almanacs and current astronomical
literature are given for the benefit of the beginner, and notes on the moon and planets, also selected lists of
interesting objects, for the convenience of the occasional observer: but the maps are rather intended to be used
as a companion to Webb’s invaluable “Celestial Objects for Common Telescopes,” and Smyth’s admirable ‘Cycle
of Celestial Objects.” Practically all the objects contained in the latest editions of these two works, down to
and including stars of the seventh magnitude, are shown in the following maps. Several fainter objects of
particular interest are added.

The “ Uranométrie Générale” of Houzeau, and certain of the catalogues of the Greenwich and Cape Observa-
tories, have also been used in the construction of these maps, so that probably few stars visible to the naked eye
have been omitted. Houzeau’s work contains the places of 5719 naked-eye stars. In the nomenclature adopted by
him, Houzeau has not been followed, nor always in his estimates of star magnitudes. The Revised Harvard
Photometry has also been consulted.

Altogether the charts indicate the positions of upwards of 6,500 stars and 600 nebule, for the epoch 1920.

Owing to the plan and arrangement of the maps, a view of about one-fifth of the entire heavens can be seen on
one folio. For this reason, and also on account of the large overlap of the maps, no constellation is inconveniently
broken up. The distortion is slight, considering the large area of the heavens represented on each chart.

It has been thought inadvisable to insert letters near the stars in order to denote their duplicity, &e. (except
“V” for variable and “R” for red), as such particulars can be more satisfactorily obtained from the lists which
must necessarily be used in conjunction with the Atlas : alllettering is made faint so as not to confuse the star groups.

The lines marking the hours of Right Ascension and every tenth degree of Declination are shown in the maps:
intermediate distances may be estimated by means of the marginal divisions which mark intervals of five minutes in
Right Ascension, and degrees of Declination.

The Author is indebted to the Publishers for several suggestions as to the form and scope of the letterpress, and
for the draft of pages 5 to 13, prepared by the Editor of the recently revised edition of the ‘Easy Guide to the
Constellations,” to which reference has already been made.

Very great pains have been taken to make the maps correct; but, where so many objects have been charted,
one cannot feel confident that no mistake has been made. The writer will be grateful to anyone who, having
detected an error, will kindly communicate with him. ,

ARTHUR P. NORTON.

Branpon Parva,

WymonpHam, Norrouk.
1910,

INDEX OF CONTENTS.

ABBREVIATIONS, List of Astronomical 4, 5
Achromatic telescope M4
Albedo of plancts
Algol (variable star)
Andromedes, The, (meteor shower)
Angular Distance, meaning of 8
Apennines, Lunar . 13, Map a ae Moon
Aperture of telescope, how measure:

7 ‘. 4

: Map 5
11

GassENDI, (lunar crater) 13
Gegenschein, The 11
8| Gibbous, meaning of 9

Globes, Celestial, ‘stars shown reversed 8
Greek Al habet, 3; star-letters, origin 5
Great Red Spot ‘of J upiter . 10

Precession, effect on signs of the Zodiac 7
Prominences, Solar, 13; how to see. 18
Protuberances, Solar 13

QuavDRATURE of planets, &c. 5 8

Rapiant Point of meteor showers . ll
‘Rays,’ Lunar (bright streaks on surface) 14

4| HaRvarD Photometry (Star Catalogue) 9 Retrograde motion, meaning of . 8
Aphelion, meaning of INFERIOR Planets . . A 9 ae Ascension rr 3 6
reer ke bl bl ) YU 3 | 2briran and moons : ‘ ee De Ted to denote stars, origin Pe
‘gus 7 (remarkable variable star) Map 10 a
Aries, First Point of, position on the ee pp ioed ia a c SavELuitEs of the Planets . 10
star sphere. . 6 Limb, of sun, moon, and planets 8 13 Saturn, and rings and moons 10
Asteroids, or Minor Planets 10) Longitude, Celestial, and difference ° | Seas, Lunar 13; also Map of Moon
Atmospheric conditions for observing 17 g 5 Senaratina pawer of telescopes 16
from Right Ascension . 8 Shooti oe ‘meteors! P' ia
ing s : ,
x = C. aoe fone ae 4, 5) Maceizanic Clouds (star clusters). 12 Sidereat Time ; : : 36
yer, Originator of Greek star-letters 5 Magnifyi f & 15] a bs
Berthon’s Dynamometer . 15,17 ying power of eye-pieces, &c. Signs of the Zodiac . . - 4,7
Magnitudes of stars, how arranged 8] Solstitial Col 8
Binary stars. 12 Table af, 3 2 sina olure ” . . :
Brightness of stars, planets, &e., Table 31M ?? outhing, meaning o :
are Imbrium (Lunar Sea) 13; Map of Moon : :
Cassini's Division of Saturn’s rings 10} Mars ( - of 9 Pai tees ete serene Saal i
pee ars iene + List of principal 4| Meridian, On the, meaning of 3 7 ing solar prominences , 18
eaning telescope lenses 5 17) Mercury . 91g ot, Great Red, of Jupiter 10
ae ua a ‘ di 14| Meteors, and List of principal showers 11 Spats én the Sun i 13
ouds, edo of . 8| Milky Way, The(see also Index Maps) 11,12] Stands. Telescope, kinds of ; 16
Clusters Ee the fae te Lists Maps 1-16} Minor Planets, and nomenclature of 10 Star, Bins ary Pr also Lists Maps 1-16
‘oal Sac e (dark gap in the Mira (variable star) . Map i Brightness of, 8: Table of 3
Milky Way) ‘ 12| Moon, (mountains, seas, craters, &c.) . Catiiognan ? 4, 5,9
Co-latitude, meaning of 6| Motion across field of a telescope . 7 » Clusters 12; also Lists iin 1-16
Colures, Equinoctial and solstitial . 8 NapiR, meaning of . 7| 4, Charts, why they get out of date 6
FN a ae toa star) i: Nembs or ie prmtipel stars a ee faintest visibl oe 3
Nautical Almanac . 9} » ow aintes visi ee.
Comets 11; comet-seeking . 18) Nebule, 12; Crab Nebula, Map 5; ‘Dumb-| ,, Naimes. ; ; ; 19
Comites (plural of comes) 12| “bell Nebula, ap 13; Gt. Andromeda] ,, Nomenclature . 5, 6, 12
Conjunction of moon, planets, &e. . 8 Nebula, Ma 3; Gt. Orion Nebula, ;, Sphere. 6
superior and inferior . 8 2
C. re 1 ti a ib wad aod 5 Map 6; Owl Nebula, Map 1; Ring Variable 12, 4; also Lists Maps 1-16
onstellations, Ancient and modern Ne ula, eee Trifid N Nebula, Map 14 Stars, To find those always visible
List of On last pa
2 P7ge)} Neptune.” and invisible from any place . 6
” Babe or: not definitely Nev Stars (1 ove) ie Stariess gaps in Milky Way - 12
agrees UPON: as 6 Node, Ascending, &e., of planet’s orbit 8 Stationary, applied to plannis, &e. . 8
pang List of astronomical . fe Nomenclature < comets 1 San, The 13; Observing the a
7 5 of meteors unspots
Counterglow, or Gegenschein 11 : of Minor Planets 10| Superior Planets. 9
Pans ies ; : y 35 of New Stars . 12| Symbols and. abbreviations, astro-
ulmination, meaning o ; , of stare : "45 nomical. : . 4
DECLINATION, ” 6 : of variable stars. 4, 5,12 Tarts of comets. 2 11
Degree on the star sphere, “ size, ” North Polar Distance A 7 Telescopes, Care of, and Cleaning . 17
and means for roughly estimating 7| North Preceding, eau of : 7 Cassegr: ainian . 14
Demon star, The (Algol) me Notes, Taking, while observing 18 ns Focal leneth, to find 15
Dew-cap, for telescopes 6| Nove, or New ‘Stars 12 : Greorea, : 14
Double stars (see also lists for each Nubecula Major, and Minor 12 non-invert image in 14
tar map) i2| Nuclona of a comet 11 i 2 us
Siar me y Lolens Oh aCOMet Inverted image in astro-
“Double-double” star in Ly ¥e Map 13) Opsncr glass of a telescope. 18, 17 i nomical 7,14, 15
Dynamometer, Berthon’s » 1,17 Occultations, difference from eclipses 12 ” Magnifying power, to find 15
Ec tipeses of sun and moon . 12 of Jupiter’s satellites 10 ss Newtonian 14
Jupiter’s satellites 10 Opposition of planets . 8, 9,10 ” Reflecting and refracting 14
Ecliptic, The 6, 7, 8, 9,11, 12) Prgasus, “Great Square” of 6,11 ” Separating power of 16
Elongation of planets, Greatest 8,9 Penumbra, i in eclipses, 12; in sunspots 13 5 Stands for 16
Envelope of a comet 1] Perigee, meaning of : ; s|, Tests for 16
Equator, The celestial 6, 7| Perihelion 3 : 8 Terminator, Moon's. : ' 13
Equatorial Stand for telescopes 16/ Perseids, meteor shower 11| Tests, Telescopic. . . 16
Equinoctial, The,7 ; Equinoctial colure 8! pjaing, Lunar : ; - 13} Transits of planets . : 8
Equinoxes, Precession of the 5,6 Planetary Nebule . : 12 of Jupiter's satel: lites . 10
Eye-pieces; how tofind magnifying power 15) Planets, Motions of 8; Notés on the 9,10) Tycho (lunar crater) 13; Map of Moon
Facut#, Solar 13 Symbols . 4, 9) Umsra, in eclipses,12; in sunspots 13
Faults, Lunar ‘ 14] Plato fioner crater) 14; also Map of Moon Uranometria Argentina (star oulogi) 9
“ Field,” or field of view ofa telescope 7,15 Pleiades (star cluster) . Map § Uranus, and moons. 10
Finder of a telescope : 16} Polaris, or Pole Star Map 2 VARIABLE stars 12; nomenclature “of 4
First Point of Aries, position on star Poles, So aloes ‘ 5 : 6 Vents 9
sphere . 6, 8| Pores, Solar. 13 :
Flamsteeds’s star uumbers, 4, 5; why Powers, Telescopic . 15| Vertex of sun, moon, and planets e
now sometimes out of order of R.A. 5 Praesepe (star cluster) Map 7 WatteD Plains (lunar). . 14
Nos. sometimes duplicate . 6| Preceding, meaning of 7| ZENITH : 7 . 7
sf Flat, ” of a Newtonian telescope . 14} Precession, of the equinoxes 5, 6| Zodiac, and Signs ofthe . - 4
Focal ‘length, To find the 15 a effect on R. A. and Dec. 6| Zodiacal Light, The é . 11

p.&

MAGNITUDES AND RELATIVE BRIGHTNESS OF PLANETS, STARS, &c.

Compared with a standard 1st magnitude star. The star magnitudes only are from the Revised Harvard Photometry.

Name of Star. ee sees Name of Star. ie sieve, Name of Star, tae a intive, Name of Star. ae Bitty ;
Sun — 26-6 |{ 8, |] Achernar ... 0°60} 1:45 || y Crucis... 1:60] 0-58 || « Sagittarii... 1:95) 0-42
Moon -— 12-2 |190,550}]) 8 Centauri ... 0°86) 1:14 || « Canis Maj. 1-63] 056 |} a Urse Maj. 1:95) 0-42
Venus... ... —4:28 | 129-4 ] Altair ... ... 089; 1:11 || « Urse Maj. 1:68] 0°53 || 6 Canis Maj. 1:98| 0-41
Jupiter* ...—2-52 | 25-59 || Betelgeuse ... 0-92] 1:08 || y Orionis ... 1:70) 0:52 || 8 Canis Maj. 1-99| 0-40
Mars*... ... — 2:25 | 19-95 Magnitude 1:00) 1:00 |) a? Centauri... 1-70] 0-52 Magnitude 2-00] 0-40
Sirius ... ... -— 1-58 | 10-77 |] Aldebaran ... 1:06] 0-95 |] A Scorpionis 1-71] 0-52 |} Polaris ... ... 2712) 0:36
Saturn*® ...—0:93 | 5-92 | Spica... ... 1:21] 0-82 [|e Carine ... 1:74] 0-51 Magnitude 2-50] 0-25
Canopus ... — 0°86 5-55 |! Pollux ... ... 1:21} 0-82 }}e Orionis ... 1:75] 0°50 3 3:00} 0-16

Magnitude 0-00 | 2-51 |] Antares... ... 1:22} 0-82 || B Tauri... ... 1-78] 0-49 i 3:50] 0-10
Vega ... ... 0-14 | 2-21 } Fomalhaut ... 1-29) 0:77 |} @ Carine ... 1-80] 0-48 a 4:00| 0.06
Capella 0-21 | 2-07 j| Arided ... ... 1:33] O-74 || a Triang.Aust.1-88| 0-44 i 4:50; 0:04
Arcturus ... 0:24 2-01 |} Regulus... ... 1:34] 0°73 || a Persei .. 1:90] 0°44 Pe 5:00] 0-03
a} Centauri 0-33 1°85 || 6B Crucis 1:50; 0°63 || » Urse Maj. 1-91] 0°43 » «+ 550} 0:02
Rigel ... ... 0-34 | 1-84 |] at Crucis 158] 0-59 |] ¢ Orionis ... 1:91] 0°43 9 --- 6°00} 0-01
Procyon 0-48 | 1°61 || Castor ... ... 1:58| 0°59 || y Geminorum 1-93} 0-42 i . 6°50] 0-006

* Mean opposition magnitudes.

DATE WHEN THE CENTRAL MERIDIAN OF EACH MAP IS ON THE MERIDIAN.
Central APPROX. DATE WHEN ON THE MERIDIAN—.e, on the line due north and south.

No. of Map. Meridian At 8 p.m. At 10 p.m. | At Midnight.| At 2 a.m. At 4 am.

Maps 3 and 4 | XXIV hrs. Nov. 21 Oct. 22 Sept. 21 Aug. 22 July 22

3 Dap 6 TV - 45 Jan, 21 Dec. 21 Nov. 21 Oct. 22 Sept. 21

si ok aye 8 VIII ,, March 23 Feb. 20 Jan. 21 Dee. 21 Nov. 21

sf Soy LO XII ,, May 22 April 22 March 22 Feb. 20 Jan. 21

a Ly TZ XVI ,, July 22 June 22 May 22 April 22 March 22

» 1d,, 14 XxX ,, Sept. 21 Aug. 22 July 22 June 22 May 22

Examples. —(1) When will the constellation Taurus be south at 10 p.m.?
we find that Taurus is in Map 5.

10 p.m., we learn that the date will be December 21.
(2) What constellations are in the south at 8 p.m. on March 25% We find the date, March 23, in the column
headed 8 p.m., and see that Maps 7 & 8 are then south, containing Gemini, Cancer, Hydra, &c.

THE GREEK ALPHABET.

Letter. Name Letter. Name. Letter. Name. Letter. Name. Letter.
eee Alpha 6 gaan Epsilon |-¢ ...... Tota ar Nu pu.
Biscaees Beta CO ssnans Zeta ee Kappa § senses Xi Oo ...
AY cetiee Gamma | 7...... Eta Aisicis'ge Lambda | o...... Omicron | 7...
O. xadaas Delta Bescsaree Theta fPswsies Mu Oe eve Pi Biaing

Name.

From the Index of Constellations
On referring to the above table, opposite Map 5, in the column headed

Letter. Naine.
Digtar ds Phi
NV aacase Chi
peer Psi
Dstaste Omega

THE HOUR OF RIGHT ASCENSION ON THE MERIDIAN AT 9 P.M.

Or Sidereal Time at 9 p.m. For each hour earlier, subtract one hour of R.A.; for each hour later, add one hour of R.A.

Date. is Date. dean Date. teas Date. hentees Date. ‘ee

at 9 p.m. at 9 p.m. at9 p.m. at 9 p.m. at 9 p.m.

h. mn, h m h. ™. h. m. h. m.

Jan. 1)| III 40]| Mar. 2} VII 40]|May 2) XI 40}! July 2} XV 40]/Sept. 1} XIX 40
» &| I¥ Of » (7/VTIL OC] 4, T/XIT O} » 7) RVE O] , 6) Se ©

» 10} ,, 20]) , 12] ,, 20 » 12] ,, 207 4, 12 ” 20)| ,, 11 zs 20

3 ES) gp BOT a 1D 9 SO a 15) 4, 30) » IS) 5 80]) y It] » 30

18! gp BO gy LE) oe SON ae DE ce SON) ce EE ge AO oye TE] ge AD

"91 ¥ ol] ,, 23/ 1X Off ,, 22/xIIr of ,, 22/XVIE of] ,, 21/XXI 0

» 26 ,, 20 » 28] ,, 20 » 27] ,, 20 » 27 ” 20 3 26 +5 20

» 28] ,, 301 ,, 30} , 307 ,, 30) ,, 307 ,, 30) ,, 307 ,, 29) 4, 30

» 31] , 40Apr. 2/ ,, 40]/June 2| ,, 40} Aug. 1] ,, 40]/Oct. 1} 5, 40

Feb, 5| VI oll, 7| X ol , 7|XIV ol, 6Ixvur ol ,, 6|xxir o
, 101 ,, 20] 2 12] ,, 20) ,, 12] ,, 20 , 12] ,, 20 , 121 ,, 20
*a2| ” 30] 2 14] 2 sol 4, 14] 5, 30, 14], 30 , 14] 2 30
a LN) og BON ge TE gg SO gg AT) gg SO gy B 40|| ,, 17 . 40
” golvir off ; 22| xr olf ,, 92) XV olf ,, 22; xIx off |, 22|xxz1r 0
” 25 20 5 28 » 20 ” 27 » 20 9 27 ” 20 , 27 PP 20
Feb. 28| VII 30 || Apr. 30| XI 30] Junc29| XV 30] Aug 29| XTX 30]| Oct. 29 |X XIII 30

Right
Date. Ascension
at 9 p.m.
h. ml.
Nov.1 | XXIII 40
» 6§/XXIV 0
” 11 ” 20
» 13) 4, 30
»y 16) 5 40
» 21} Ih 0O
» 26} 4, 20
» 29; 4, 30
Dec. 1 » 40
» 6] II 0
” 11 9° 20
» 14) 4, 30
” 16 ” 40
» 21) III Oo
2 27) 9 20
Dec.29| III 30

Dec. = Declination

ei ae oe see

a:
i ee oi

Greek Letter (to a star). Bayer’s designation in his Celestial Atlas, 1603, or that of Lacaille.

Small Roman Letter (to a star). Bayer’s designation in his Celestial Atlas, 1603, or that of Lacaille.

Roman Capitals R to Z (to a star). Usually variable stars, except in a few Southern Constellations where there
are no Flamsteed humbers. In Cygnus and Virgo these letters, having all been used up, were repeated in
the double form RR, RS, RT, &. In the case of Cygnus, the double combinations of letters from R to Z
have now been exhausted, and the series AA, AB to AQ, BB, BC to BQ, and so on, are being assigned, as
the variable stars are discovered. Another system in use is to denote the variable by a single letter with

Thus: RS=S? Cephei, ZZ = Z® Cygni.

The number in Flamsteed’s “ British Catalogue,” published in 1725.

Number only (to a nebula). The number in the New Edition of Sir J. Herschel’s General Catalogue of Nebule

Number underlined (to a star). The number in Piazzi’s Catalogue of 1814. [and Clusters.

Numbers, as 391, 34¢ (to a nebula). Sir W. Herschel’s Nos., and the classes into which he divided the nebule.

The small crosses (+) in the maps indicate points of intersection of intermediate 20m. of R.A., and 5° of Dec.

(+ =North Dec. | N.P.D.= North Polar Distance. | R or Ru. (small, to a star) = Red or Ruddy.
= South Dec.) | R.A. = Right Ascension. V or Var. (small, to a star) = Variable.

an index number added.
Number only (to a star).

Mag. = Magnitude b=

STAR CATALOGUES.

Contraction. With number added, = Number in— Contraction. With number added, = Number in—
Arg. . Argelander. (See B.D. below). RR: . Revised Harvard Photometry, 1908.
B ... Birmingham’s Catalogue of Red Stars, 1877. | Jac. . Jacob’s Catalogue of Double Stars, 1849.
B.A.C. ... British Association Catalogue of 1845. ee ong Catalogue of Southern Stars, pub-
Argelander’s Bonn ‘ Durchmusterung,” eM co lished by the British Association, 1847.
es { ”1859-62.* ” | TL... Lalande’s Catalogue, pub. by the B.A., 1837.
ee ... Burnham’s Double Star Catalogues. M ... Messier’s Catalogue of 103 Nebule, pub. 1784.
: Bris. {°" T. Brisbane’s Catalogue of Southern Stars, | P. ... Piazzi’s Star Catalogue, 1803-1814.
a Rus .. Russell’s Double Star Measures (Sydney), 1891.
C.G.A. ... Gould’s “ Catalogo General Argentino,” 1886. | g _ South’s Measures of Double Stars, 1826.
A es Dunlop’s Catalogues of Double Stars and | g, _.. Santiago Observations, 1876.
| i — ae : S.M.P. ... Harvard Southern Meridian Photometry,1895.
EB Espin’s Edition of Birmingham’s Catalogue =
of Red Stars, 1888. St ao s Cape Catalogue for 1880, or Radcliffe
Pra A : : Catalogue for 1890.
Gr. ‘2 Sages See i ea ee ee ee a. Uranometria Argentina, 1886.
u Sir W. Herschel’s Catalogues of Double Stars, IE Serer 2 gaged ey aerate Nova Oxoniensis, 1885.
sof 1782-1822. 5 F. G. W. Struve’s Dorpat Catalogue of Double
Houz. .. Houzeau’s Uranométrie Générale, 1878. Stars, 1837.
h Sir J. Herschel’s Catalogues of (1) Nebule, =I 4 Do. do. Append |.
a of 1833, 1847; and (2) of Double Stars. | OZ . Otto Struve’s Revised Pulkova Catalogue, 1850.
H.P : Pickering’s Harvard Photometry, 1884. Ozz . Pulkova Catalogue, Part II.
ASTRONOMICAL SYMBOLS.
Conjunction Opposition Quadrature Perihelion Ascending node Descending node
O 8 ro)
THE SIGNS OF THE ZODIAC.
Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Sagittarius Capricornus Aquarius Pisces
, fe) u ore R 1 = mM 8 os ad
THE SYMBOLS OF THE PLANETS.
Sun Mercury Venus Moon Earth Mars Jupiter Saturn Uranus Neptune
OMG =o - oot G2 One 6 u h HI 3

* In this case the zone is stated as well as the number.

Thus B.D. +13° 2302 means Star No. 2302 in the 13° zone, north, in the B.D.

p. 4.

NORTON’S STAR ATLAS.

ADDITIONS AND NOTES.

On the presumption that Herschel’s New General Catalogue
(1888) is correct, the places or descriptions of the following
nebulee and clusters are given incorrectly in the 2nd (1881)
Edition of Smyth’s Cycle of Celestial Objects, from which they
were taken for this atlas. They should, therefore, be erased or
altered on the maps. Mr. Chambers, the editor of Smyth’s Cycle,
has kindly given permission for this list to be issued with his
approval, although he has not had time to verify all the items.

48” CassIOpEI& is 1° further N. - . - (Map 2).
101M Ursa Masortis is 2° further N. (Maps 2, 9, and 11)
58! is S. Decl. and not N. in Taurus - == (Mapa):
258! is N. Decl. and not S. in Horonoarum (Maps 6 & 15).
61° Aurige®. Decl. N. is 18’ less - = (Map 5):
508 Monocerotis. Decl. is N. not S.. - - (Map 8).
308 Puppts is 10° further N. : - - (Map 8.)
1711 Com Ber. should read 175! - - - (Map 9).
21! Virarnis should read 24! - - - (Map 9
75? ViraInis is 1° further S. - - (Map 9).

61! Virernts should read 68! (
f Lurt should read d Lupi (
51! DeLpHtni should read 52! - . - (Map 18).
236 Saqirrarit is 1° further N. - - (
167 Dunlop Dorapts is 3° further S. - (

NOTE.
The star lettered ¢ CepHer (Houzeau) is generally given
as v (Map 2).
ADDITIONAL CONTRACTIONS.
G.C. Sir John Herschel’s General Catalogue of Nebulie and
Clusters (1864),
N.G.C. A New General Catalogue of Nebulae and Clusters of
Stars, being the above catalogue, revised, corrected, and
enlarged by J. L. E. Dreyer (1888).

Ay pan Ape us

FOR SMALL TELESCOPES.

I.—NOTES ON STAR NOMENCLATURE, &c.

The Constellations.—The origin of most of the constellation names is lost in antiquity. Coma Brrenicrs was
added to the old list (though not definitely fixed till the time of Tycho Brahé), early in our Era; but no further
addition was made till the seventeenth century, when Bayer, Hevelius, and other astronomers, formed many constella-
tions in the hitherto uncharted regions of the southern heavens, and marked of portions of some of the large or ill-
defined ancient constellations into new constellations. Many of these latter, however, were never generally recognised,
and have been dropped altogether, or had their names abbreviated into more convenient forms. Since the middle of
the eighteenth century, when Lacaille added thirteen additional names in the southern hemisphere, and subdivided
the unwieldly Arco into the more convenient Carina, Matus, Puppis, and VELA, no new constellations have
been recognised. (See list of constellations at end of book).

Star Nomenclature.—The Star Names given in the list on pagel9 have for the most part been handed down
from classical or early medieval times, but only a few of them are now in common use, it having been found more
convenient to adopt the plan introduced by Bayer in 1603, viz.—the designation of the bright stars in each constel-
lation by the ordinary letters of the Greek Alphabet, a, 8, y, &e. When there were more stars than Greek letters,
Roman letters, both ordinary and capital, have also been employed. As the Roman capital letters, however, were
not generally used except in the constellations of the far south, the convenient plan has recently been introduced of
denoting the principal variable stars in each constellation by the Roman capital letters near the end of the alphabet
—R, 8, T, U, V, &c., thus affording a ready index to their peculiarity. After Z is reached, the letters are dupli-
cated thus—RR, RS, &e.

The fainter stars are most conveniently designated by their numbers in some star catalogue. By universal con-
sent, the numbers of Flamsteed’s British Catalogue (published 1725) are adopted for stars to which no Greek letter
has been assigned, while for stars not appearing in that catalogue, the numbers of some other catalogue are utilised.
For convenience of reference, the more important star catalogues are designated by recognised contractions: thus,
“B. A.C. 2130” is at once known by astronomers to denote the star numbered 2130 in the British Association Star
Catalogue, published in 1845. A list of some of the best-known catalogues, and their contractions, is given on p. 4.
In most star catalogues a number is assigned to each star included in them, whether it has a Greek or other
letter, or not. Thus, Vegais a Lyre, 3 Lyrm (Flamsteed’s number), and Groombridge 2616, the latter catalogue
being arranged in order.of Right Ascension, no notice being taken of the constellations.

Flamsteed arranged his stars by constellations, and numbered them according to their order in Right Ascension
—a convenient form for reference, as the stars follow a regular sequence. Occasionally, however, stars numbered in
order of Right Ascension, in course of time become displaced from this order, owing to the precession of the Equinoxes
(or “precession,” as it is termed for short). This happens if their Right Ascensions are nearly the same, and if they

are widely different in Declination.
B 5

6 NOTES ON STAR NOMENCLATURE, €c.

Constellation Boundaries.—These have never been definitely agreed upon, so that occasionally Flamsteed and
others numbered stars in one constellation which in other catalogues or charts are included in a neighbouring
constellation. Thus 24 and 26 Cametoparpi of Flamsteed are included in Prrszus in the present work,
Occasionally, also, in assigning Greek letters, stars were included by mistake in ¢wo constellations. For example,
B Tauri and y AvurRic# are one and the same star. The same thing occasionally happens in star catalogues:
Flamsteed, for instance, is known to have duplicated half a dozen stars.

II. NOTES ON ASTRONOMICAL TERMS.

The Star Sphere is an expression used for convenience in speaking of the heavenly bodies and their positions
with respect to one another. The name is derived from the appearance presented by the heavens as seen from the
earth, the earth being apparently at the centre of a vast hollow sphere, which makes a complete revolution every day,
and to the inside surface of which the stars seem fixed—for they do not sensibly change their place relatively to one
another, in spite of their daily revolution. Of course, only one-half of the star sphere can be seen, at the same
moment, from any place on the earth.

The pivots, as it were, of this sphere—the celestial poles—are directly overhead at the terrestrial poles; and its
equator—half-way between the poles—is directly overhead at the terrestrial equator, so that it is easy to measure the
positions of the stars by saying they are so many degrees north or south of the celestial equator (called the stars’
“Declination ”), and so many degrees east or west of some meridian. The latter distance, however, is for convenience
expressed in hours and minutes of time instead of degrees, as explained below, and is termed “ Right Ascension.”

Right Ascension.—The Right Ascension of a star (contracted ‘‘R.A.”) corresponds to the longitude of a place
on the earth’s surface. The starting point is known as “The First Point of Aries,” a point in the sky situated on
the celestial equator, nearly as far below y Pecast as a ANDROMEDZ is above it—stars forming one side of what is
known as “The Great Square of Pegasus ”—or a little below the small star w of Piscgs.

As the heavens circle completely round the earth once each day, it is easy to note how many hours, minutes,
and seconds elapse between the time at which this point ‘culminates’ (¢.e. attains its highest altitude above the
horizon, see p. 7) and the time of culmination of any desired star. This interval is called the star’s Right Ascension.
Thus every star which culminates ati the same instant as the “First Point of Aries,” is said to have a Right Ascen-
sion of 0 hours, 0 minutes ; all that culminate three hours later are said to have a Right Ascension of three hours, and
similarly for any other interval, up to twenty-four hours, which is the same as 0 hours, 0 minutes. Strictly speaking,
these hours, minutes, and seconds of Right Ascension are respectively very slightly shorter than the hours, minutes,
and seconds of ordinary clocks, because the stars make a complete circuit of the earth in 23 hours, 56 minutes, 4’seconds,

“or in about four minutes less than a mean solar day. Observatories are provided with special clocks, regulated to keep.
this sidereal time, for reading off the exact instant of culmination, of planets, comets, &c., and thus finding their R. A.

In more scientific language, the First Point of Aries is the point in the sky at which the centre of the Sun
crosses the celestial equator at the vernal equinox in March, but yearly it changes its position slightly among the stars,
moving back on the Ecliptic 50}” of arc per annum (=about 3 seconds of R.A.), or a space equal to the apparent.
diameter of the Moon in about thirty-nine years. Though it retains its old name, it is no longer in the constellation
of Aries but in that of Pisces. This is why star charts get out of date: the starting point of measurement is not.
fixed, and both the Declination and Right Ascension lines in the chart after a while no longer represent the
actual positions with reasonable accuracy, especially near the Celestial Poles. This backward motion is ‘precession.’

Declination.—The Declination of a star (contracted “Dec.”) corresponds to terrestrial latitude, and is
measured by the number of degrees the star is north or south of the Celestial Equator, which is simply an extension,
as it were, of the terrestrial equator as far as the star sphere. As already mentioned, at the terrestrial equator the
celestial equator is directly overhead; and similarly at any latitude on the earth’s surface, the stars with the same
amount of Declination as the latitude will be directly overhead when culminating. The signs + and — are some-
times used instead of N. and &., to distinguish between North (+) and South Declination (— ).

Stars with a greater declination than the co-latitude”of the observer never set, but are always above the horizon,
if both observer and star are on the same side of the equator, or never rise if they are on opposite sides of the
equator. Thus in latitude 50° north, all stars with declination north greater than 40° never set, and those with

declination south greater than 40° never rise above the horizon.
*The difference of the latitude from 90°.

NOTES ON ASTRONOMICAL TERMS. 7

*

North Polar Distance.—Sometimes the latitude of a star is measured from the North Celestial Pole instead

of from the celestial equator: in this case it is termed its ‘North Polar Distance,’ and ranges from 0° at the North
Pole to 180° at the South Pole.

“Size” of a degree on the star sphere.—The following will be found useful for roughly estimating

angular distances on the star sphere: others can easily be made up from the star charts. The degrees are those of
a “great circle,” such as degrees of declination, or degrees measured along the celestial equator :—

Half a degree = approximately the angular diameter of the Moon.
1} degrees = approximately the angular distance between 6 and « Orionis.

2 ” = ” ” ” ” ” vw and Y AQUILE.

24 ” ai ” ” ” ” ” a and B AQUILE.

a Pe es + 3 » aand ® Canis Minoris; or 8 and ¢ Crucis.
5b yy = Pe Rs 3 ‘3 » aand B Ursm Masoris.

The Ecliptic, shown on star charts, indicates the path traced out by the centre of the Sun as it travels among
the stars in its (apparent) annual circuit of the heavens. That is to say, if we could see the Sun and the stars
behind it at the same moment, day by day we should find the Sun exactly following the line shown on the charts.

The Equinoctial is another name for the celestial equator.
The Zenith is the point in the sky directly over the observer's head ; the nadir that directly below his feet.

The Zodiac is a belt of the sky, extending 8 degrees on each side of the Ecliptic, in which the Moon and the
principal planets are always to be found. It is divided into twelve ‘Signs,’ each 30 degrees in length, denoted thus—
Aries Taurus Gemini Cancer Leo Virgo Libra Scorpio Sagittarius Capricornus . Aquarius Pisces
ay b a (ore) S Ty oe TH 3 V8 a, ad

As the result of precession, the signs of the Zodiac do not now coincide with the constellations of the same name.

Culmination, &c.—A star is said to culminate when it reaches its highest point above the horizon of the
observer. In the Northern Hemisphere this invariably takes place when the star is due south, in the Southern
Hemisphere when it is due north. The phrases, ‘on the meridian,’ or ‘returns to the meridian,’ have the same
meaning as culmination. In northern latitudes this is sometimes termed “Southing.”

‘Lower culmination’ (used in connection with circumpolar stars only, 2.e. stars which never set), indicates their
position twelve hours after ordinary culmination, when nearest the horizon, at the opposite side of the celestial pole.

North Preceding, &¢.—In describing how to find celestial objects, the often-used phrase “ North (or South)
Preceding,” “North (or South) following,” a certain star, means that the object is nearer the North or South celestial
pole than the star referred to. “ Preceding ” means that its Right Ascension is less than, and “following” greater
than, that of the reference star, and indicates the direction in which to find the required object.

Observers in the Northern Hemisphere must remember that in the inverted view of an object, as seen in
astronomical telescopes (except “Gregorians,” see p. 14), the upper part of the field of view is south, while the
lower part is north. To observers south of the Equator, however, the reverse is the case.

Between rising and culmination. Soutbing or culminating. Between culmination and setting.
(Angle depending on latitude of observer and declination of star.) (Upright.) (Angle depending on latitude of observer and declination of star.

n. p.=North preceding, .f.=North following. ». p. =South preceding. 3. f.=South following. P=West. F=East,

Diagram showing direction of motion of a star across the field of an inverting astronomical telescope used in the Northern
Hemisphere, In the Southern Hemisphere, hold the book upside down.

In the diagram, the arrow denotes the apparent path of a star as it crosses the field of view of a fixed telescope
in the Northern Hemisphere. This path will be horizontal only when the object is on the meridian, but the relative

positions remain unchanged.
in the sense of distance north or south of the celestial equator.

i i a to its terrestrial meanin:
a ee eas ee nena Z planet, &., is its distance in degrees north or south of the

But ‘latitude’ in astronomy has quite a different meaning ; the ‘latitude ’ of a
ecliptic. See the paragraph on Longitude on the following page.

8 NOTES ON ASTRONOMICAL TERMS.

Longitude.—-This term, when used in astronomy, must not be confused with Right Ascension, from which it is
quite different. Both Longitude and Right Ascension start from the First Point of Aries, but the former is measured
(0 to 360 degrees) along the ecliptic ; the latter along the celesttal equator, in hours, &c.—1 hour being exactly equal to
15 degrees, and 4 minutes exactly equal to 1 degree. As the ecliptic lies at an angle to the celestial equator, the
result is that a planet’s movement of 1° in longitude does not exactly correspond to 1° (i.e. 4 minutes) in Right
Ascension, partly because the direction of measurement is different, and partly because the respective degrees may
be of different lengths on the star sphere—as, for instance, where the ‘great circle’ degrees of the ecliptic itself
traverse the ever-narrowing Right Ascension degrees (i.e. 4 minutes) at Declination 20°.

The term ‘longitude’ is now only used astronomically in connection with planets and comets, and is the angle
between the First Point of Aries and the foot of a perpendicular line drawn from the planet, d&c., to the ecliptic.
It is more convenient than Right Ascension for describing the circuit of planets round the star sphere, because all
the principal planets follow the course of the ecliptic rather than the celestial equator.

Motions of the planets.—A planet is in perihelion (7) when it is at its nearest distance to the sun, and in
aphelion when it has reached its greatest distance from it. Perigee is the point of the moon’s orbit which is nearest
the earth, and apogee that which is most distant from it; but the terms are sometimes applied to the planets in the
same sense. Planets are in conjunction (6) with the sun, moon, or another planet, when their longitudes are the
same—Mereury or Venus being in superior conjunction with the sun when the conjunction occurs while they are
on the far side of sun from the earth (7.¢. the sun being between the planet and the earth), or in inferior conjunction
if they are on the near side of the sun. ‘Conjunction’ is also sometimes used to denote similarity in Right Ascension.

Mars and the planets beyond—Jupiter, Saturn, &c., are in opposition (symbol §) when their angular distance on
the star sphere away from the sun is 180° of longitude (or 12 hrs. R.A.), so that they are on the meridian about
midnight ; and in quadrature (() when they are 90° of longitude (or 6 hrs. R.A.) from it, thus being on the
meridian about 6 a.m. or 6 p.m. Planets are said to to be stationary, when their seeming movement east or west
among the stars is changing to the reverse direction, and retrograde when their seeming motion among the stars is
westerly instead of easterly. The elongation of a planet is its angular distance (i.e. its distance in degrees) from the
sun as seen from the earth; the greatest elongation of Mercury or Venus being the time when this angular distarice is
at its maximum. Transits of Mercury and Venus occur when, from the earth, they are seen passing over the sun’s disc.

When a planet, in its movement among the stars, reaches the ecliptic on the star sphere—that is, in reality,
reaches the plane of the ecliptic—it is said to be at a node of its orbit. If it is passing from the north to the south
side of the ecliptic, it is at the descending node, (symbol 25); if the reverse, at the ascending node (symbol (2). The
nodes, in fact, are the points of intersection of the planet’s orbit with the ecliptic.

Albedo.—The albedo of a planet, is its light-reflecting capacity per unit of area—actual, not angular area. It
varies considerably, for, according to Zéllner, Mercury reflects "138, Venus ‘50, Mars -27, Jupiter -62, Saturn ‘52,
Uranus °64, Neptune 46, and the Moon ‘174, of the light which they respectively receive from the sun. Other
estimates of Venus are even brighter. The albedo of terrestria! clouds is estimated at about -72.

Vertex.—The vertex of the moon, sun, or a planet, is the point on its ‘limb’ or edge furthest above the horizon
of the observer. When measuring distances in degrees from the vertex, they are counted eastwards from 0° round

to 360° again.

Colures.—These will be found marked on celestial globes, &c. The eguwinoctial colure is the great circle passing
through the celestial poles and the First Point of Aries (or ‘equinox’ as it is otherwise called), and is the same as the
circle of 0 hrs. and 12 hrs. of Right Ascension. The solstitial colure is the great circle of R.A. 6 hrs. and 18 hrs.

It may be noted here that the stars on celestial globes are reversed as regards left and right; because a globe
necessarily represents the star sphere as seen from the outside, while we view the stars from the inside of the star sphere.

Star Magnitudes.—The brightest stars are said to be of the first magnitude ; those less bright, to be of the
second magnitude; those still less bright, to be of the third magnitude, and so on. Each magnitude is about 24
times as bright as the one below it, a standard first magnitude star (e.g. Aldebaran, Altair) being exactly one
hundred times as bright as a standard sixth magnitude star—which last is the faintest that can be seen with the

NOTES ON ASTRONOMICAL TERMS. 9

naked eye. As, however, several first magnitude stars are much brighter than Aldebaran, it has been found
necessary, in modern magnitude valuation on a scientific basis, to still further extend the range of magnitudes, a star
of magnitude “0” being about 2} times as bright as one of magnitude 1, and one of magnitude minus 1, being
about 24 times brighter than one of magnitude “0.” Intermediate magnitudes are denoted in tenths; thus mag-
nitude 3-0 is slightly brighter than 3:1, but less bright than 2°9. The brightest fixed star, Sirius, has a magnitude
of -1°6. The Moon on the same scale is magnitude —12:2, Venus, the brightest of the planets, -4:28, and the
Sun —26°6. (See Table on p. 3).

The sixth magnitude, as already mentioned, is about the faintest visible to the naked eye; the eleventh, ina
three-inch telescope, and the seventeenth, in the most powerful telescopes yet constructed.

Star Catalogues.—These are very numerous and of every description—for stars, double stars, clusters, nebule,
variable and coloured stars, &c., but are rather inaccessible to the ordinary observer, many being found only in the
journals of scientific societies, and others being very expensive. A selection of the more important catalogues is given
on p. 4; a long list will be found in Vol. II. of G. F. Chambers’ ‘Handbook of Astronomy.’ For star
magnitudes the best known works are Pickering’s Harvard Photometry, the Revised Harvard Photometry and
its supplement (1908)—which together contain the magnitudes, &c., of no fewer than 45,792 stars in both
hemispheres—and Gould’s Uranometria Argentina (Southern Hemisphere).

III. NOTES ON THE PLANETS, STARS, NEBULA, &c.

The Planets.—These cannot be inserted in star charts as their positions are continually varying, but the
Nautical Almanac, or some other based upon it, or the lists in newspapers and magazines, give their Right Ascensions
and Declinations from day to day, so that their places among the stars can easily be found.

The principal planets always keep within a few degrees on either side of the Ecliptic, and may be distinguished
from fixed stars by the fact that they do not twinkle, except ozcasionally when very low down. They are denoted
by the following symbols :—

Sun Mercury Venus Moon Earth Mars Jupiter Saturn Uranus Neptune

©orO g g ( ® or é 3 yf h i sa

Mercury and Venus, which are nearer the Sun than the earth, are called the ‘inferior planets’; Mars and the other
planets beyond it are termed the ‘superior planets.’

Mercury keeps so close to the Sun that it is not readily observed, its maximum greatest elongation from the Sun
being only 273°. Even under the most favourable conditions, therefore, it is only visible for about two hours, at
most, after sunset or before sunrise, and at a low altitude above the horizon, especially in higher terrestrial latitudes.
It is best seen about the time of the equinoxes, when these coincide with its ‘greatest elongations,’ (see above).
The disc of Mercury exhibits the same phases as the Moon, and varies in angular diameter from 4$” to nearly 13”.

Venus is the brightest of the Planets, and can sometimes be seen in broad daylight. In a small telescope, its
chief interest is that it also has phases like the Moon—some of which can be discerned even with an opera-glass.
The dazzling brightness of Venus renders observations of its surface-markings very difficult. It should be examined
in the daylight, or as soon as possible after sunset or before sunrise. It appears brightest during the ‘crescent’ phase—
as an evening star about a month after, and as a morning star about a month before its greatest elongation.

Venus attains a maximum elongation from the Sun of 47 degrees, and the angular diameter of its disc varies
from 10” to 65”. At its brightestit is about 12 times as bright as Sirius, the brightest fixed star.

Mars is not usually well seen in small telescopes, but at favourable ‘ oppositions, —z.e. when the earth is on the
line between it and the Sun, and the two planets are thus at their nearest to one another—dark green markings are
discernible on the ruddy disc, and generally a white spot at one of the poles, probably due to snow. The most favour-
able oppositions occur at intervals of about fifteen or seventeen years (in 1894, 1909). In certain positions, Mars is
seen slightly ‘gibbous,’ ¢.e. not fully illuminated, but in ‘opposition’ it presents a round disc. Angular diameter
34” to 30”, and mean opposition magnitude — 2-25, or fully a half magnitude greater than Sirius.

10 NOTES ON THE PLANETS, STARS, NEBULA, ée.

Jupiter is a splendid object for small telescopes, ‘parallel belt’ markings being plainly visible on its disc, which
is perceptibly elliptical in shape. The ‘Great Red Spot’ marking, 30,000 miles long, 7000 broad, discovered in 1878,
was of a bright colour till 1881, when it began to fade away. In 1892 it was of a pale orange tint, but ill-defined,
and invisible in small instruments. The spot is now (1910) invisible, but a faint bay or hollow in the belt still
marks its position. ,

Jupiter’s angular diameter varies from 28” to 46”, and its mean opposition magnitude is — 2°52, or about twice
as bright as Sirius.

Four of Jupiter's satellites, or ‘moons,’ are visible in an opera-glass, all being about magnitude 6; the
others only in giant telescopes. Three of these satellites are eclipsed by Jupiter’s shadow once every
revolution, but they do not disappear instantaneously, as the motion is slow. Sometimes a satellite ‘transits’ or
passes across the face of the planet, app2aring at the beginning or end of the transit as a bright spot on a dark back-
ground (the ‘limb,’ or edge, of the planet’s disc being darker than the centre), while at intermediate times it may
disappear from view altogether, if the background happens to be similar in brightness and colour, or it may appear
asa dark spot. The shadows of the satellites also transit the planet’s disc, showing as dark spots, which are apt to be
mistaken for the satellites themselves; sometimes both satellite and shadow may be seen transiting at the same time.
Occultations, which ozcur when the satellites pass behind the body of Jupiter, are frequent, but generally of little interest.

The configuration of the larger satellites throughout the year is given in almanacs. They are numbered
consecutively I., II., IIT., IV., in order of distance, I. being nearest the planet.

Saturn is also a magnificent object for a small telescope; faint parallel-belt markings may be discerned, but
its special feature is its wonderful ‘ring’ system, divided into two by a hair-like dark line known as ‘‘Cassini’s Division,”
just visible in a 2} in. refractor when the rings are widely open. Other divisions of the ring can sometimes be seen
in very larg: telescopes. At intervals of about fifteen years (from 1908) the rings present their edge to the earth,
and become invisible for a short period. Saturn’s angular diameter varies from 15” to 20”, and its mean opposition
magnitude is — 0°93—rather brighter than that of Canopus, the second brightest fixed star.

Saturn’s brightest satellite, Titan, shines as a star of the 9th magnitude, and may be seen with a very small
telescope, while four other satellites—Rhea, Iapetus, Tethys, and Dione—are within the reach of a 4-in. instrument,
and may sometimes be glimpsed with an aperture of 3-in. or even less. They are of about the 11th magnitude.

Uranus app2ars as a star of the sixth magnitude to the naked eye. Its disc, having an angular diameter of
only 34”, and also its satellites, are only distinguishable in large telescopes.

Neptune can be seen with the aid of an opera-glass when its position is found by reference to an almanac and
the star charts, but is a faint and uninteresting telescopic object. Its angular diameter is 24”, and its magnitude at
opposition 7:8.

The Asteroids, or Minor Planets, are mostly very minute. The positions of the largest are given in the
Nautical Almanac. They are numbered according to their order of discovery, and are printed thus though
names are also giventhem. The brightest of the asteroids are about magnitude 6} to 8 at time of opposition.*

*In 1892 it was decided to distinguish the asteroids provisionally by letters which were afterwards used in a doubled form AA, AB.
The double alphabet has been used up, and recently discovered asteroids have been designated JE, JF, JG. The permanent number is
assigned when the orbit has been determined. . The numbered asteroids now amount to 674 (Jan. 1910).

NOTES ON THE PLANETS, STARS, NEBULZ, ée. 11

Comets vary in brightness, most of them being visible only with the aid of a telescope. A comet is generally
first discernible as a minute, faint, misty patch of light, so much resembling a nebula that it is only identified as
a comet when found to be in motion, but sometimes even a very large comet escapes detection at first by approaching
us in the line of the sun. The essential portion of all comets is the coma or head, the misty patch of light already
mentioned. In addition a nuclews may develop as it approaches the sun, 7.e. a bright fame-like or star-like appear-
ance within the coma, and also a tail, or sometimes several tails—which always point more or less away from the sun,
no matter whether the comet is approaching or receding from the sun. The tail usually appears as a curved hollow
cone, decreasing in brightness as it widens out. Both nucleus and tail, when present, increase in size and brightness
as the comet nears the sun, and decrease as it recedes from the sun; envelopes, or stratifications of the mist round
the nucleus, especially on the side towards the sun, may also appear as the comet approaches perihelion. Neither
nucleus nor tail, however, are necessarily present. Many comets are known to be connected in some way with
meteoric showers. Periodic Comets are those which revolve round the sun and appear to us at more or less regular
intervals.

New comets are denoted by the year in which they are discovered. Thus Comet a 1909, was the first discovered
that year, and Comet 6 1909, was the second, and so on. They may also be designated by the order in which they
arrive at the perihelion ; thus Comet V 1909, which means the fifth comet that arrived at perihelion during that
year.

Meteors, or Shooting Stars, may appear in any part of the sky, but it is found that there are certain well-
marked points on the star sphere from which showers of meteors come every year at regular dates, when the earth
returns to the same part of its orbit. These showers are named from the constellation in which the ‘Radiant Point’
or ‘Radiant’ lies—so called because it is the point in the sky from which the meteors of the shower appear to
radiate in all directions. Meteors are twice as frequent at 6 a.m. as at 6 p.m., because at the former hour we are
facing in the direction of the earth’s motion in its orbit, while in the latter we are facing to the rear. Radiants have
not been inserted in the charts, but the following are a few of the principal showers that may be looked for, and the
approximate position of their Radiant Points :—

Date of Shower. Name. ae . ne " Date of Shower. Name. — me gions
h. in. h. m.
Jan, 2-3 Quadrantids |15 20) 53° N, July 25-30 6 Aquarids 22 36) 11° S.
aoe AGT « Cygnids 19 40) 53° N. Aug. 10-12 Perseids 3 0] 57° N.
Feb. 5-10 a Aurigids 5 0} 41° N.j} Aug. 12-Oct. 2 v Aurigids 4 56] 42° N.
April 20-22 Lyrids 18 4) 33° N. Aug.—Sept. Lacertids 22 «8 | 49° N.
May 6 y Aquarids 22 32) 2°58. Oct. 2 Bodtids 15 20] 52° N.
a. ad u Coronids 15 24] 27° N. Oct. 18-20 Orionids 6 8| 15° N.
» 30 7 Pegasids 22 12) 27° N. Nov. 18-15 Leonids 10 0} 22° N.
J une—Sept. y Draconids 17 56| 48° N. Nov. 17-27 Andromedes 1 40| 43° N.
July—Aug. Cygnids 21 0; 48° N. Dec. 10-12 Geminids 7 12} 33° N.
July 25-Aug, 4 a-8 Perseids 3 12] 43° N.

Note.—The Perseids, Orionids, Geminids, and several other showers, are visible every year about the time given.
The Leonids, or November Meteors, were plentiful in 1799, 1833 and 1866, being seen at their best at intervals of
about 33 years. In 1900 the display was not brilliant, owing to the disturbance of their orbit by the planet Jupiter.

The Zodiacal Light is not well seen in temperate latitudes, except near the time of the equinoxes. It appears
as a faint, hazy, conical, beam of light which follows the course of the ecliptic on the star sphere, for 90° or more
from the horizon where the sun has set (in spring), or will rise (in the autumn). It has been estimated as being, in
its brightest parts, two or three times as luminous as the Milky Way, and is most probably due to sunlight reflected
from meteoric bodies revolving round the sun. Its brightness seems to vary from time to time, and towards its
extreme limits it is always exceedingly faint. Owing to its vertical, or almost vertical, position and the short dura-
tion of twilight, it is brighter when observed within the tropics than in temperate latitudes.

The Gegenschein or ‘counterglow’ is very difficult indeed to see; it appears as a very faint round patch of
light, 10° to 20° in diameter (i.e. larger than the ‘Great Square of Pegasus’=a, 8, y, Pucast and a ANDROMEDS),
situated on the ecliptic at the point diametrically opposite to where the sun is for the time being. The best

12 NOTES ON THE PLANETS, STARS, NEBULZ, ée.

chance of seeing it is on a moonless night of exceptional clearness, when the ecliptic is highest above the horizon,
viz., in December and January, but it cannot be distinguished if projected on the Milky Way. It also is possibly
due to sunlight reflected from meteoric bodies.

The Milky Way* extends like a girdle right round the star sphere. Between Cyenus and Scorpio it forms two
narrow parallel bands; thereafter for a considerable distance it is very much broken up and complex in form, but
brighter. When Canis Masor is reached it becomes a single but fainter band, until in Cyenus it is joined again. The
telescope shows that it is composed of myriads of minute stars, of the tenth and eleventh magnitude on the average.

There is a remarkable gap (starless to the naked eye) in the Milky Way, near the foot of Crux, in the Southern
Hemisphere, to which the name of ‘The Coal Sack’ has been given: it presents the appearance of a dark abyss in the
midst of the surrounding brightness. There is a similar but smaller starless gap in Cygnus, and others elsewhere.

The Magellanic Clouds, or Vubecula Major and Vubecula Minor, appear to the naked eye like detached portions
of the Milky Way, and are a marvellous sight in the telescope, being made up of nebule and star clusters, both
regular and irregular in shape. Their respective positions are R.A. 5h. 30m., Dec. 70° S., and R.A. Oh. 50m.,
Dec. 73° S., and they are therefore not visible from the latitude of Europe or the United States.

Double Stars are stars which to the naked eye appear as a single point of light, but when viewed through a
telescope are found to be composed of two stars—or more, in the case of triple, &c., stars. Where one of the stars is of a
much smaller magnitude than the other it is often styled a comes (plural comites) or companion.

Binary Stars are double stars which have been proved to revolve round a common centre of gravity.

Variable Stars are those which wax and wane in intrinsic brightness. Except in some southern constellations,
the principal ones are frequently distinguished in star nomenclature by the Roman capital letters at the end of the
alphabet, R, 8, T, &c., the double form RR, RS, RT, &e., being used after Z is reached. (See note, top of p. 4).

Nove, or New Stars, are stars which suddenly blaze out in places where no star visible to the naked eye has
been known before, and then gradually fade away. They are designated by the year in which they appear, thus,
Nova, 1866. If more than one appears in any year, they are numbered Nova 1, Nova 2, and so on.

Star Clusters are portions of the sky in which the stars are crowded very closely together.

Nebule are faint, misty, patches of light, usually of irregular form. Some of these have been resolved by the
most powerful telescopes into patches of exceedingly minute stars ; others are known to be masses of incandescent gas.
Planstary Nebule ave circular in form—so called because they much resemble the disc of a planet as seen in a telescope.

Occultations take place when the moon or a planet passes directly between us and some other heavenly body,
shutting it out from view. Occultations of stars by the moon are frequent, and their times are given in almanacs: the
disappearance always takes place on the east side of the moon and the reappearance on the west. Where the star
occulted is bright, the disappearance and reappearance, being instantaneous, are of great interest. Zclipses of
satellites, as distinguished from occultations, take place when they enter the shadow of their planet, and become
invisible merely because the sun no longer shines on them, although nothing intervenes between them and us.

Eclipses.— 7'otal and annular solar eclipses are so rarely visible from any given place that they need not be
described in detail. Under the most favourable conditions, about three to four hours elapse between first and last
contact, but the total phase never exceeds eight minutes in a total eclipse, or 124 minutes in an annular eclipse, and is
usually much less. At the equator, both totality and contact interval last about a quarter longer than at latitude 50°.

Partial solar eclipses are of little interest unless nearly total. In a small telescope, the sun appears as if it had
‘a circular notch of greater or less size cut out of it.

Lunar eclipses, when total, last about four hours, from first to last contact, of which totality is for about two
hours. Through the telescope, the earth’s shadow may be seen sweeping slowly across the moon’s disc, but its edge
is not sharply defined. Usually the moon does not altogether disappear from view, even at mid eclipse, but shines with
a dull reddish-orange light, being illuminated by sunlight refracted by the earth’s atmosphere: the colour and bright-
ness of the illumination depend on the amount of water vapour and clouds present in the earth’s atmosphere at the time.

The wmbra, in solar and lunar eclipses, is the dark shadow on that portion of the earth or moon which, for the
time being, receives no direct light from the sun. The umbra shades away into the hordering penumbra, or partial
shadow, which covers those regions whence the sun would be seen partially eclipsed.

* See Index Maps.

NOTES ON THE PLANETS, STARS, NEBULZ, ée. 13

The Sun, as an object for small telescopes, is of little interest unless sunspots are visible: special precautions
are required in observing it so as not to injure the eyesight (see p. 18).

In large telescopes the disc of the sun presents a granular or ‘rice-grain’ appearance. Even in a small
telescope of 2 or 3 inches aperture, the surface of the sun will shew a mottled appearance, when the air is steady and
definition good ; but this mottling is of a coarser texture than that delicate granular appearance seen under higher
powers with large instruments. Facule, i.e. irregular patches somewhat brighter than the average, may generally
be seen. They are found on every part of the disc, but are best seen near the ‘limb’ or edge of the sun’s disc, owing
to the decrease in brilliancy of that part, arising from the sun’s absorbent atmosphere.

Sunspots vary in size from small ‘ pores,’ as the smallest are termed, to groups so large as to be occasionally
visible to the naked eye. They present the appearance of a dark irregular spot, or uwmbra, surrounded by a
less dark portion, or penumbra; the umbra, however, is only apparently dark, by comparison with its surroundings,
being actually brighter than the electric arc. Sunspots are never seen at the sun’s poles, and rarely at its equator,
but are mostly confined to zones extending about 20° on each side of the solar-equator. They wax and wane in
number and intensity, at times none being visible, attaining a maximum or minimum about every eleven years,
with some intermediate minor fluctuations. Special interest attaches to them from the fact that there is a connection
between them and terrestrial magnetism—as yet unexplained.

The sun’s rotation may be traced day by day by the apparent motion of the spots across the disc, the rotational
period being about 25 days near the equator, and 27 days at 45°. Spots may thus be visible for almost a fortnight
at atime. Occasionally they are visible as a small notch on the sun’s edge, when just coming into view from the
far side of the sun.

Prominences or protuberances are jets or clouds of glowing red gas which rise all round the sun’s ‘limb’ or edge.
They can be seen only during total eclipses, or by means of a spectroscope attached to the telescope. (See p. 18).

The Corona, also seen only during total eclipses, is a mysterious, irregular, pearly halo of light surrounding the sun.
It is never quite the same, either in shape or extent, in successive eclipses, and appears to be partly gaseous, and
partly meteoric, for it shines partly by reflected sunlight.

The Moon is the most interesting of all the heavenly bodies for a small telescope. In an opera-glass the dark
portions visible to the naked eye are seen to be the smoother portions of the moon’s surface, the remainder of the
surface is a mass of craters of every size, from some of which brilliant white streaks radiate for a great distance.

The best time for viewing the moon is when it is about its first or last quarter, as the lunar mountains near the
terminator (or boundary between the bright and dark portion) then cast long sharp shadows which give a fine effect
of contrast with the bright portions. At the time of full moon this contrast is lost. A low power should be used
in the first instance for a general view.

The moon always presents the same side to the earth, so that one side of the moon is never seen at all. Owing,
however, to what is termed the moon’s libration, or apparent swaying, owing to the inclination of its axis to its
orbit, and to other causes, we sometimes see a little more on one side or another, so that altogether about six-tenths of
the surface is visible at one time or another. A full description of the moon with its great wealth of details is quite
beyond the scope of the present work, but the following paragraphs, together with the sketch-map (see frontispiece)
indicate the principal features.

Lunar plains, the darker and smoother portions of the surface, were supposed by the early telescopists to be
seas—which they much resemble under very low powers—and were named accordingly. More perfect instruments,
however, revealed that the supposed seas were simply vast plains, by no means level, or smooth, possibly once the
bottom of lunar oceans.

Lunar mountain ranges and peaks are much higher in proportion to the moon’s diameter than terrestrial ranges
are to the earth’s diameter, some of them attaining a height of about five miles. The most conspicuous range is
The Apennines, in the northern hemisphere of the moon, which rises like a wall from the Mare Imbrium. It is about
600 miles long, and its highest peaks attain a height of 34 miles—the heights being found by measurements of their
long sharp shadows, nearly 100 miles long.

Lunar craters, which are such a prominent feature in lunar landscapes, are of all sizes from a hundred and fifty
miles in diameter downwards. Craters proper have one or more conical peaks within the crater walls, of which

Tycho and Gassendi are fine examples ; those which have a smooth level bottom, without central peaks, and with
c

14 NOTES ON THE PLANETS, STARS, NEBULA, ée.

. lower bounding walls than the craters proper, are called walled plains, of which Plato is the best example. The
interiors of the craters are usually lower than the surface outside, but sometimes the reverse is the case. Frequently
an old crater will be seen that has been broken into by a later one.

Lunar rills are deep, winding, narrow valleys, resembling the bed of a dried up stream. Lunar clefts appear like
cracks on the smoother portions of the surface. It is difficult to realise that these hairlike markings are sometimes
fifty or a hundred miles long and up to 24 miles in width. The greater number of clefts are to be seen only in pretty
powerful telescopes. Faults are closed cracks in the moon’s surface, and are numerous. They are visible owing to
the surface on one side of them being higher than that on the other.

Lunar rays are the bright streaks which radiate from some of the principal craters. Unlike other lunar features,
they are best seen about the time of full moon. The finest system of rays radiates from the great crater Tycho, in
the southern lunar hemisphere. The strangest feature of these rays is that they are everywhere on the same level as
the rest of the surface, and traverse unbroken both crater walls, valleys, and seas. No fully satisfactory explanation
of their nature has yet been given.

IV. THE CARE AND USE OF THE TELESCOPE.
THE following brief notes are given in the hope that they may be of use to the inexperienced observer :—

Telescopes are of two kinds—refracting and reflecting. Both varieties are rated according to their “aperture,”
as the clear diameter of the large lens in refracting telescopes, or of the mirror in reflecting telescopes, is called.

The larger the aperture, the more powerful the telescope in rendering visible faint objects; and, as this power in-
creases in proportion to the square of the diameter, a telescope of 3 inches aperture is more than twice as powerful
as one of 2 inches, while a 4-inch aperture is nearly twice as powerful as a 3-inch, or four times as powerful as a two-
inch one—the actual ratios being 4, 9, 16. For astronomical purposes, a 3-inch telescope may be considered as about
the smallest that can be used with satisfaction, though pleasing views of many objects may be obtained with even
smaller telescopes of good quality.

THE REFRACTING TELESCOPE.
The astronomical refractor essentially consists of two convex lenses—(i) a large one of considerable focal length,
known as the object glass, which forms at its focus an image of the distant star or other object, and (ii) a small lens of
much shorter focal length: this is called the eye-piece, and is used to magnify the image formed by the object glass.

The Object Glass.—This is the most important part of the telescope, as its excellence depends on the accuracy
of the curves of the lenses, the highness of their polish, and their transparency. In all astronomical telescopes
worthy of the name, the object glass is “achromatic ;” that is to say, it is composed of two (sometimes three) lenses
of equal size but made of glasses of different density. These are so proportioned as to form an image almost free from
the false colours, which are inevitably present when a bright object is viewed through an object glass consisting of a
single Jens. A good object glass requires to be treated with the most scrupulous care, and the notes on the care of
the telescope on p. 17 should be carefully followed.

THE REFLECTING TELESCOPE.
In this form of telescope a large, concave, parabolic-curved mirror takes the place of the object glass of the
refracting telescope.
The large mirror is held in a cell at the lower end of the large tube. The rays of light from the object pass
down the tube and are reflected back. The reflected, convergent rays are intercepted—

(1) In the “ Newtonian ” form of telescope by a small, elliptical, plane mirror, or “flat,” which reflects them at
right angles through the side of the telescope to the eye-piece.

(2) In the “Gregorian” form by a small concave mirror, or (3) in the “Cassegrainian” form by a small convex
mirror, which reflects them back again, through a hole in the centre of the large mirror, to the eye-piece.

The Newtonian and Cassegrainian forms give an inverted image, similar to that of the refracting telescope: the
Gregorian, however, gives an erect image.

THE CARE AND USE OF THE TELESCOPE. 15

EYE-PIECES.

As already mentioned, these are used to magnify the image formed by the object glass, or the large mirror.
For very high powers, and in special cases, a single lens is sometimes used ; but generally an eye-piece consists of two

lenses, mounted in a short tube which screws or slips into the focussing-tube of the telescope. There are several
varieties, but the most common are :—

The Huyghenian or negative eye-piece.—This is the most common form, and consists of two plano-convex
lenses; having their flat surfaces towards the eye.

The Ramsden or positive eye-piece.—Which gives a ‘flatter’ field than the Huyghenian (z.e. the field of view
visible through it is not so blurred around the edges when the centre is sharply focussed), and, when of
achromatic construction, performs excellently on planets.

As seen in an astronomical telescope with either of these eye-pieces, an object is inverted. To make it appear
the right way up involves the use of additional lenses, which means some loss of light and a slightly fainter image,
without any compensating gain.

The magnifying power of a telescope depends entirely upon the ratio of the focal length of the object
glass to that of the eye-piece: thus, with an object glass of 36 inches focal length, and an eye-piece having a focal
length of 4 inch, the magnifying power will be 72 diameters, or “ power 72” as it is termed.

It is advisable to have at least three eye-pieces of different power :—

(1). One of low power with a large “field,” (that is, showing a considerable area of the sky), for viewing comets,

large and scattered clusters, and extended nebule, magnifying 8 or 10 times per inch of aperture. Thus,
on a 3 in, telescope the power may be from 25 to 30.

(2). One of moderate power, magnifying 25 or 30 times to each inch of aperture.
(3). One of high power, magnifying 50 or 60 times to each inch of aperture.

When experience has been gained, the observer may sometimes use eye-pieces of still higher power, but, as a
rule, to advantage only on close double stars, when the telescope is of excellent quality and the atmospheric conditions
are most favourable. The extreme limit of useful power is about 100 diameters per inch of aperture. It must be
remembered that, as the power is increased, a corresponding apparent increase takes place in any defects of the
telescope, the vibrations of the stand or ground, the rate of motion of a star across the field, and of atmospheric
disturbances.

To find the focal length of the object glass or mirror.—Remove the eye-piece, and stretch a piece of
semi-transparent paper over the end of the draw-tube. Point the telescope at the sun, and focus the sun’s image on
the paper screen. The measured distance between the back of the object glass and the screen is, for practical
purposes, the focal length of the object glass. In the Newtonian Telescope, the distance is measured from the centre
of the surface of the large mirror to the centre of the surface of the flat, and thence to the screen, placed as above.

To find the focal length of a Huyghenian eye-piece.— Divide twice the product of the focal lengths of
the two lenses by the sum of their focal lengths: the quotient is the focal length of an equivalent single lens.

To find the power of an eye-piece.—Make a scale with plainly-marked equal divisions. Set this up at a
considerable distance away, and, holding both eyes open, view the scale through the telescope with one eye and
directly with the other. The number of divisions on the scale, covered by the magnified image of one of them, is
equal to the magnifying power of the eye-piece used. For measuring low powers, a distant brick wall will take the
place of the scale.

Another method.—Focus the telescope on a star. Next morning, without altering the focus, point the telescope
to the bright sky. When the eye is placed about 10 inches behind the eye-piece, there will be seen a small, clearly-
defined disc of light. Measure the diameter of this dise by means of a Berthon Dynamometer (see p. 17) placed
against the eye-piece—a pocket lens, of low power, should be used as an aid in doing this. The magnifying power of
the eye-piece is found by dividing the clear diameter of the object glass by the measured diameter of the bright
image.

Diameter of field.—To ascertain the diameter of the field of an eye-piece, observe how long a star situated

16

THE CARE AND USE OF THE TELESCOPE.

near the equator (e.g. 5 Ortonis) takes to pass centrally across the field from one side to the other. This time, ex-
pressed in minutes and seconds, when multiplied by 15, will give the diameter of the field in minutes and seconds of arc.

TESTS.

The actual performance of a telescope on a celestial object is the only really satisfactory test. Seen through a
telescope bearing its highest power, a fixed star of the second magnitude should appear as a minute, well-defined,
circular disc of light, almost a point, and surrounded by one or two thin, concentric, bright rings. There should be
no false rays of light, and the rest of the field should be uniformly dark. The telescope should not, however, be con-
demned too hastily, as an inferior eye-piece, or the state of the air (see p.17), may be responsible for apparent defects
in the object glass. A close double star with very unequal components forms a most severe test. A telescope of the
finest quality should separate a double, consisting of two 6th magnitude stars, whose distance from centre to centre in

seconds of arc is equal to 4:56 divided by the aperture expressed in inches: thus, a 3-inch telescope should just divide

a double star whose components are 1°52” apart.

ACCESSORIES.

Stands.—Much depends upon the rigidity of the telescope stand, and good observations must not be expected
from the open window of an ordinary room, as the vibration of the floor, and the mixed currents of air, set the

Improvised Equatorial.

object being viewed dancing. For small telescopes, the ordinary, alt-azimuth, tripod
garden stand is most convenient. An iron pipe of about 4 inches diameter, partly
sunk in the ground, and rammed full of clay to deaden vibration, forms a good support
for a telescope of moderate size.

The “equatorial” stand is of enormous advantage, but is rather expensive. It has
one of the pivots, or axes, which carries the telescope, directed towards the celestial pole,
(being adjustable for latitude). The result is that a star may be followed by a single
circular movement of the telescope, instead of the instrument having to be moved both
in altitude and azimuth.

A tolerably satisfactory makeshift can be arranged (in the higher latitudes at least)
with an ordinary tripod stand, by setting one leg to the pole-star, and then adjusting the
other legs so that the pillar of the telescope-is-tilted over to point to the pole-star.

Or still better, by screwing on to the top of the stand a block of wood which is cut
off at an angle, as shown in the illustration (A), and which has a V-groove, with sides at
an angle of 60°, cut along the inclined face, for receiving the pillar. The claw legs of the
stand, folded up, will act as a counterpoise, and two or three screw clamps will keep the
pillar firm. <A piece of hard wood (not shown in the illustration), also V-grooved, should
be interposed between the point of the screws and the pillar, to prevent damage when
tightening up the screws. A somewhat simpler construction is to hinge this upper block
at one side to the lower block, and pass the screws through both blocks at the other
side, as shown in the illustration at (B).

The angle of the sloping top, from the vertical, must be the latitude of the observer subtracted from 90°. Thus,
for latitude 52° it will be 90° - 52° =38°.

Finder.—A finder is a small telescope fixed by supports to the body of the larger instrument. When high
powers are used, this adjunct is a necessity, and in all cases it adds much to the comfort of observing. The finder

may be roughly adjusted by day on a distant weather-cock or some other definite object. To improve the adjustment,
bring the polar star into the centre of the field of a low power eye-piece on the large telescope; then alter the direc-

tion of the finder, by means of the adjusting screws, until the star image is in the centre of the field of the telescope,

and also bisected by the cross wires of the finder at the same moment. Now replace the low-power eye-piece by one

of high power, and perfect the adjustments in the same way. For small telescopes up to 3-inch, ‘sights’ similar to

those on rifles can be arranged (painted white), which will be found of some service.

Dew-cap.—To guard against the deposition of dew on the object glass, make a tube of tin, cardboard, or some
such material, about 9 inches or 1 foot long, and of.such a diameter as to fit closely, but not too tightly, on to the

object glass end of the tube.

The inside of the dew-cap.should be covered with black velvet, or painted with a

mixture of lamp-black and size.

THE CARE AND USE OF THE TELESCOPE. 17

Berthon’s Dynamometer (or measuring gauge) is a little instrument used for measuring the diameters of
small objects. It has two flat metal sides, the internal straight edges of which meet towards the end, and are inclined
to each other at a small angle. One of the edges is graduated from 0 to 2, of an inch. The figures on the scale

: denote the width of the gap between the two straight

edges. To measure the diameter of any small object
by means of this little appliance, it is only necessary

to see at what part of the scale the object just fills
HORNE & THORNTHWAITE

BERTHON'S DYNAMOMETER. LONOON

the space between the internal edges of the gauge,

and then take the reading from the scale. The
scale is divided into 20 long divisions of -01 or hundredths of an inch These are subdivided into five parts each
equal to -002 or five-hundredths of an inch. The first two long divisions are again divided into parts equal to ‘001
or thousandths of an inch. The price is 7/6.

HINTS ON CLEANING.

Refracting Telescope.—A good object glass is so delicately figured that it should be cleaned as rarely and
carefully as possible, for fear of affecting the accuracy of its form. (See below, “Cleaning.”)

The lenses should never be taken out of their cell by an inexperienced person.

The object glass should be held in its cell with just sufficient “play” for a slight rattle to be heard when it is
gently shaken. If screwed up tightly, it causes strains in the glass which mar the perfect definition.

Reflecting Telescope.—The silvered mirror requires to be kept with very special care, as the silver is exceed-
ingly liable to tarnish, especially in or near large towns, from the sulphurous fumes in the air. The owner of a
reflecting telescope should, therefore, procure and study the “Hints on Reflectors,” which have been published by
several of the leading makers of these instruments.

A slight stain causes merely an inconsiderable loss of light, but, if badly tarnished, the mirror must be re-silvered.
This process may be successfully accomplished by the amateur, with little difficulty, and at no great expense, if he
carefully follows the directions given in the books just referred to, and uses pure chemicals.

Care of the Telescope.—Before removing the telescope after the night’s work, cover the object glass or mirror
with the metal cap provided for that purpose.

Never take the instrument from the cold outer air into a warm room, or the object glass will become dewed.
If this should happen, the object glass must not be left in that state; but it should be placed in a warm room, at a
safe distance from a fire, until the moisture has vanished. Any stains left on the glass must be removed by gentle
polishing. Never wipe an object glass when it is damp.

Cleaning the Lenses.— When it becomes necessary to clean these, any dust should first be removed by means of
a camel’s-hair brush. Then the lens should be wiped very gently with a piece of very fine and clean wash-leather or
silk.

When not in use, all brushes and materials employed for this purpose should be carefully protected from dust
by keeping them in clean stoppered bottles or air-tight cases.

HINTS ON OBSERVING, &c.

Atmospheric Conditions.—To get the best results, objects should be viewed when they are as far as possible
above the horizon, i.e. when near culmination. Satisfactory observations cannot be made of objects at low altitudes,
owing to the increased intervening thickness of the atmosphere, and the haze and mist which so often obscure the
horizon. The nights when the sky is darkest, and the stars most brilliant, are by no means always the best for
observational purposes. Faint and ill-defined objects, such as some nebule, may, however, often be seen to advan-
tage on nights of this class.

When the stars twinkle much it is an indication that the air is unsteady and not altogether satisfactory for

observation.
During a slight haze, the air is often very steady, and splendid views of bright objects may then be obtained.

18 THE CARE AND USE OF THE TELESCOPE.

Viewing Faint Objects.—The eye becomes much more sensitive to faint impressions after it has been kept
in the dark for a considerable time.

Very faint objects, otherwise invisible, may sometimes be detected by averted vision: the eye is directed to
another part of the field, while the attention is fixed on the spot where the object is supposed to be.

A slight change of focus is often restful to the tired eye.

Viewing the Sun.—It is extremely dangerous to attempt to view the sun unless proper precautions are taken:
blindness may be the penalty of rashness or ignorance. A perfectly safe method is to support a smooth, white card,
at the distance of about a foot from the eye-piece, and to focus the image of the sun projected on it. The screen
should be held in a covered frame-work or box, and the picture of the sun viewed through a hole in one of the sides.
If, on the other hand, the sun is viewed directly through a dark-glass cap, a larger aperture than 2 inches cannot
safely be used in the heat of summer. A stop made of a card, with a circular hole of 2 inches or less in diameter,
should be fitted over the object glass of a larger instrument, to reduce the amount of light and heat transmitted.

To see the prominences by means of the spectroscope, the edge of the sun’s image should be made to fall on the
nearly-closed slit of the spectroscope—which must be one of considerable dispersive power. The telescope should then
be driven (preferably by clock-work) so as to keep the image in the same position. The spectroscope is next focussed
on one of the hydrogen lines of the spectrum, and, on the slit being opened, the prominence will be seen. Good
views may be obtained in this way, using a 3-inch telescope with a spectroscope having several prisms.

Comet-seeking.—In searching for comets, a telescope of fairly large aperture and of short focal length, with an
eye-piece of low power having a large field of view, should be used. The observer should slowly ‘sweep’ (2.e. move
the telescope in a horizontal direction) for some distance, a careful watch being kept all the time. At the end of
the sweep the telescope is slightly raised or lowered, and an overlapping sweep is taken in the opposite direction.
This process is repeated continuously. Should a nebulous-looking object be noticed, the comet-hunter must look in
his catalogue of nebule to see if the object can be identified. If not, he should draw a careful sketch of its position
among the neighbouring stars. If in the course of time any movement can be detected, and the place of the sus-
pected object does not agree with that of any known comet, its position should be determined as accurately as means
will allow, and a telegram giving particulars should be sent to the Astronomer Royal, Greenwich Observatory.

Making Notes, Consulting the Charts when observing, &c.—A bull’s-eye lantern with a slide to shut
off the light is of great use.. A cycle lamp may be utilised by the occasional observer. It may be placed on a
support at some distance from the observer, and so directed as to throw a faint light on the book or card, when
notes or sketches are being made at the telescope.

A strong light should be avoided as it makes the eye less sensitive for observation.

A small table to hold the maps and other books, with a lantern having a shade to throw the light downwards,
lest the direct rays of light should reach the eye, is almost a necessity.
A) observations should be written down at the time when they are made. The notes should be clearly worded,
and should have entered on them the year, month, day, hour, and minute of the observation, together with the
aperture and power of the telescope and the state of the air.

LIST OF STAR NAMES.

Name, =
Achernar ... a Eridani.

Acrab, Akrab B Scorpionis.

Adara .. € Canis Majoris.
Albireo iis ... B Cygni.
Alchiba, Al-khiba ... . a Corvi.
Alcor 80 Urs Majoris.
Aleyone (a Pleiad) . 9 Tauri.
Aldebaran ... .-. a Tauri.
Alderamin ... ..u Cephei.
Algeiba, Algieba .. y Leonis.
Algenib : ... y Pegasi.
Algol aie tats ... B Persei.
Algorab, Algorel, Algores ... § Corvi.
Alhena y Geminorum.
Alroth .. € Urse Majoris.

Alkaid (Benetnasch) » Urs Marjoris.

Alkalurops ... pf Bodtis.
Alkes a Crateris.
Almak, Almach y Andromede.
Alnilam sei e Orionis.
Alphard (Cor Hydre) wu Hydre.

Alphecca, Alphekka a Corone Borealis.
Alpheratz, aaa é Rincheamiete:

(Sirrah)
Alphirk ...B Cephei.
Alrai (Errav) ...y Cephei.
Alruccabah (Polaris) a Urs Minoris.
Alshain, Alshairn ... B Aquile.
Altair a Aquile.
Alwaid 8 Draconis.
Antares (Cor Scorpionis) o Scorpionis.
Arcturus ies .. a Bodtis.
Arided (Deneb Adige) . a Cygni.
Arneb uv. Leporis.
Asterope (a Pleiad) ..21 Tauri.
Atlas (a Pleiad) 27 Tauri.
Azelfafage ... ... 7! Cygni.

Azimech (Spica)
Baten Kaitos
Bellatriz ...

Benetnasch ... ...9 Urse Majoris.
Betelyeux, Betelgeuze a Orionis.
Canopus .. a Argis.
Capella a Aurige.
Caph, Chaph 8 Cassiopeiz.
Castor a Geminorum.

Cor Caroli... a Canum Venaticorum.
Cor Hydre (Alphard) _ ...« Hydre.
Cor Leonis (Regulus) _... a Leonis.

a Virginis.
¢ Ceti.
y Orionis.

Name. =
Cor Scorpionis (Antares) « Scorpionis.

Cor Serpentis (Unukalhay) a Serpentis

Cursa, Kursa B Eridani.
Deneb, Deneb Aleet, :
Denebola 5 } B Leonis.

Deneb Algiedi
Deneb, Deneb el Adige :

(Arided) } Wrens
Deneb Kaitos shemali t Ceti.
Diphda (Deneb Kaitos jenudi) B Ceti.
Dubhe

§ Capricorni.

.. u Urse Majoris.

Electra (a Pleiad)... ..17 Tauri.
Enif, Eniph (Fom) .. € Pegasi.
Errai (Alrat) ...y Cephei.

Ltamin, Etanin
Fom (Enif)

Fomalhaut ...

y Draconis.
.. € Pegasi.
a Piscis Australis.

Gemma a Corone Borealis
Giedi a. Capricorni.
Gomeisa £8 Canis Minoris.
Hamal a Arietis.
Homam, Homan ... ... ¢ Pegasi.
Lzar (Mizar, Mirac) . € Bootis.
Kattain (Okda) a Piscium.

Kaus Australis e Sagittarii.
Keid 40 Eridani.
Kelb al Rai, Celb al Rai @ Ophiuchi.
Kocab, Kochab _... 8 Ursee Minoris.

Kornephoros B Herculis.
Kursa, Cursa 8 Eridani.
Maia (a Pleiad) ...20 Tauri.
Markab ... a Pegasi.
Marsik « Herculis.
Mebsuta. e Geminorum.
Meyrez ... 6 Urse Majoris.
| Mekab, Menkab, Menkar ... a Ceti.
Menkalinan B Aurigze.
Merak ...B Urse Majoris,
Merope (a Pleiad) ... ...23 Tauri.
Mesarthim, Mesartim ...y Arietis.
Mintaka 6 Orionis.
Mira o Ceti.

Mirac, Mirach ... 8 Andromedae.
Mirac, Mirach (Izar)
Mirfak, Mirphak ...

. € Bodtis.

Mirzam B Canis Majoris.
Mizar ... 8 Andromede.
Mizar = . € Bodtis.
Mizar ... € Urse Majorir

.. @ Persei. :

Name. =
Muphrid ... a ... 9 Bootis.
Nath - .. 2 Tauri.
Nekkar ... B Bodtis.
Okda (Kaitain) wu Piscium.
Phakt, Phact a Columbee,

Phecda, Phekha ... y Urse Majoris.
Pleione (a Pleiad) ... ... 28 Tauri.

Polaris ..a Urse Minoris.
Pollux 8 Geminorum.
Prima Giedi a! Capricorni.
Procyon a Canis Minoris.
Pulcherrima ... © Bobtis.

Ras Algethi, Rasalegti a Herculis.

fas Alhagua, Ras-al-hague aOphiuchi.

Rastaban, Rasaben y Draconis.
Regulus (Cor Leonis) .. u Leonis.
Rigel B Orionis.
Rotanev B Delphini.
Sadachbia ... y Aquarii.
Sadalmelik, Sadalmulk a Aquarii.
Sadalsud, Sadalsund 8 Aquarii.
Secunda Giede a? Capricorni.
Scheat, Sheat ... B Pegasi.

Schedir, Shedir, Schedar a. Cassiopein.
Sheliak .. B Lyre.
Sheratan, Sharatain B Arietis.
Sirius — ...a Canis Majoris.
Strrah (Alpheratz)
Skat, Sheat, Scheat

u Andromede.
6 Aquarii.

Spica a Virginis.
Sulaphat . y Lyre.
Svalocin u Delphini.
Talitha, Talita . t Urse Majoris.
Tarazed y Aquile.
Taygeta (a Pleiad) ...19 Tauri.
Thuban ian vu Draconis.
nukalha :
et ieee tall } u Serpentis.
Vega, Wega oa Lyre.
Vindemiatria « Virginis.
Wasat 6 Geminorum.
Yed 6 Ophiuchi.
Zaurak y) Eridani.

Zawyah, Zavyava B Virginis.

Zosca, Zosma ... 5 Leonis.

Zuben el Genubi . a Libre,
Zuben el Hakrabi ... .. y Libre.
Zubenesch, Zuben el) Alito

Chemali, Zubenelg |
19

TELESCOPIC OBJECTS—MAPS 1 & 2.

DOUBLE STARS.

9 Cassiope1£. Oh. 44m. N. 57° 25’. A binary star. Period 196 years. Magnitudes 4 and 74. Distance
5‘7” (1903). Colours, yellow and pale red.

o Cassiopriz, 23h. 55m. N. 55° 20’. A double star. Magnitudes 54 and 74. Distance 3”. A grand field
with a low power.

Cepnnt 21h. 27m. N. 70°15’. A 3rd mag. star with a bluish 8th mag. comes, 14” distant.

CrepHer 22h, 2m. N. 64° 15’. A double star. Mags. of components 5 and 64. Distance about 7”

Op UH BD

CepuEr. 22h. 26m. N.58°0’. A fine double star. The brighter star varies from 3:7 to 5 mag. in a period of
dd. 83h. The companion is a 5th mag. blue star, 41” distant.

v Draconis. 17h. 30m. N. 55° 15’. A double star composed of two 44 mag. stars. Distance 62”.

¢ Urs# Masoris (Mizar). 13h. 20m. WN. 55° 20’. The middle star of the Great Bear’s tail. A splendid
double star with components of the 2nd and 4th magnitudes and 14” apart. It forms with 80 (Alcor),
about 11’ distant, a naked-eye pair. Several fainter stars are included in a large field.

a Urs Minorts (Polaris). lh. 32m. N. 88° 50’. The Polar Star. In 1920 it will be about 1° 7’ from the
north celestial pole, and in the year 2095 within 26’ 30”. It is a 2nd mag. star with a 9th mag. bluish
attendant 19” distant, a well known test for instruments of less than 3 in. aperture. Polaris can easily be
found by means of the “ Pointers,” a and B Urse Majoris.

7! Urs® Mrnoris. 15h. 35m. N. 80° 40’. A double star, north preceding (. Components of the 6th and
7th mags. Distance 30”.

VARIABLE STARS.
u CePHEL 21h. 41m. N. 58° 25’. An irregular variable star “of a fine deep garnet colour.” (Sir W.
Herschel).

Nova Casstoperz. Oh. 20m. N. 63° 40’. The New Star of 1572 which equalled Venus in brilliancy and then
died away. The place should be carefully watched for a possible reappearance.

NEBULE & STAR CLUSTERS.

H. VI. 30 CassioPeie. 23h. 53m. N. 56°15’. A beautiful cluster of small stars. Grand neighbouring fields.

M.52 Cepuy. 23h. 21m. N. 61°10’. An irregular cluster containing an orange-coloured star.

H.IV. 37. Draconis. 17h. 59m. N. 66° 35’. A remarkable, bluish, elliptic, planetary nebula. It lies near the
N. Pole of the Ecliptic, between the Polar Star and y Draconis.

M. 97. Ursa Masoris, 11h.10m. N. 55° 30’. A large, remarkable, planetary nebula with a faint disc, of the
apparent diameter of Jupiter. The “Owl Nebula” of Lord Rosse: so called from its appearance in his
great reflector.

MAPS 1 anp 2
(Circumpolar, North )

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ABBREVIATIONS
Greek letter (to a star,) Bayer's designation.
Small Roman letter ,, as «
» capitals R to Z (to a star,) Variable stars.

Number only (to a star,) Flamsteed’s number.

i (to neb.,) Sir J. Herschel's No. (New Ed.)
Number underlined (to a star,) Piazzi’s No.
Number with small no. | Sir W. Herschel’'s

to right of it. (to neb.,)! mumber and class. s 97@

B.A.C. British Association number,
Burnham's number.

Br. Brisbane's number.
Aa Dunlop’s number.
E-B Espin and Birmingham's number.
H Sir W. Herschel’s number.
h Sir J. Herschel’s number.
Jac. Jacob’s number.
Lac. Lacaille’s number.
LI. Lalande’s number.
M Messier's nebula number.;
OZ Otto Struve’s number.
OZE Pulkowa Cat, Pt. 1. No,
Ror Ru, (small, to star).

» Ruddy or yellow star.
Rus. Russell’s number.
Sa. Santiago number.
St. Stone's number.
‘= ,_F. Struve's number.
Zi.” =Do, App'dix I. do.
V or Var. (small, to star)

= Variable star.

MAP 2

MAGNITUDES

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TELESCOPIC OBJECTS—MAPS 3 & 4

DOUBLE STARS.

a AnpRomEDs. Oh. 32m. N. 33°15’, A double star. Components of the 4th and 8th mags. Distance 36”.
y ANpRomeps. lh. 59m. N. 41° 55’, A magnificent double star. An orange 3rd mag. star with a blue
5th mag., 10” distant. The smaller star is itself a very close double. 1889, almost closed ; 1902, 0-25”.

41 Aquari. 22h. 10m. §. 21° 30’. A double star consisting of a reddish 6th. mag, star with a blue 8th
mag., 5” distant.

¢ Aquari. 22h. 25m. §, 0° 25’. A very fine object ina small telescope. Its distance of 4:5” in 1780 had
closed to 3” in 1892. Magnitudes 4 and 4:1. A binary star.

y! Aquari. 23h. 12m. 8. 9° 30’. A wide double star (50”). The brighter star is of mag. 44, and
yellow ; the other 84 mag., and blue. .

8 Lacerts#. 22h,32m. N. 39°10’. A quadruple star, whose components are of the mags. 6, 64, 10 and 9.

e« Preast. 21h. 40m. N.9° 30’. A triple star, but only a wide double in small telescopes. Magnitudes 2} and
9. Distance 140”,

aw! Precast. 22h.6m, N. 32° 45’. Forms with 7? a fine wide pair.

ym Precast. 22h. 40m. N. 29° 45’. A 3rd mag. star with a 10th mag. companion, 90” distant. A test for a
3-inch telescope.

35 Piscrum. Oh. llm. N. 8° 20°. A double star. The components are of about the 6th and 7th mags.
Distance 11:5”.

t TRIANGULI. 2h. 8m. N. 29° 55’, A lovely double star. Its components are of mags. 5 and 63. Distance
3°6".

VARIABLE STAR.

o Cett (Mira). 2h. 15m. 8. 3° 20’. A wonderful irregular variable star, which changes from 14 to 94 mag-
nitude.

NEBULA & STAR CLUSTERS.

M. 31 Anpromepm. Oh. 38m. N, 40° 50’. The Great Nebula. Visible to the naked eye, preceding ». In
small telescopes, an oval, hazy mass. Photographs show it as a wonderful spiral.

H. VIIL 75, Lacert#. 22h. 12m. N. 49° 30’. A fine cluster, with a beautiful field following it.

MAPS 3 anp 4
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DOUBLE STARS.
y Arieris. 1h. 49m. N. 18°55’. A double star discovered by Hooke in 1664. Magnitudes of each com-
ponent, 44. Distance 8-6”. A fine object.

y Cet. 2h. 39m. N. 2°50’. A 3rd mag. yellowish star with a 7th mag. companion. Distance 2-6”.
32 Eripant. 3h. 50m. 8. 3° 10’. A double star. The brighter component is of the 4th mag., and yellow:
the fainter 6th mag., and blue or green.

y Leports. 5h. 41m. 8. 22° 30’. A triple star. The chief components are of mags. 4 and 64, and 93”
distant. A third faint star is 45” from the 64 mag.

8 Ortonts (Rigel). 5h. 11m. S. 8° 20’. A star of the lst mag. with a bluish 8th mag. attendant, 9” distant.
Well seen in 2}-inch Wray.

t Orronis. 5h. 381m. 8. 5° 55’. A double star. Magnitudes 3 and 7. Distance 11”.

o Orntonts. 5h. 34m. 8. 2° 40’. A multiple star. The chief components are of the magnitudes 4, 10, 74, and 7.

52 Orntonis. 5h. 44m. N. 6° 25’. A double star, consisting of two equal 6 mag. stars at 1:5” distance (1906).
A hard test for 3 in.

» Perser. 2h. 44m. N. 55° 35’. A yellow 4th mag, star, with a blue attendant of 8} mag. Distance 28”.

a Tauri (Aldebaran). 4h. 31m. N. 16° 20’. A star of the Ist mag. with an 11th mag. attendant, 109”
distant. A good light-test for a 3 in. telescope.

VARIABLE STARS.
B Psrser (Algol). 3h. 3m. N, 40° 40°. The Demon Star. This notable variable has a period of 2d. 20h.
49m. Its usual magnitude for about 24 days is 24. In nearly 34 hrs. it decreases to 3-6 mag., and after
remaining at that for 18 or 20 minutes, in another 3} hrs. it regains its former brilliancy.

NEBULA & STAR CLUSTERS.
M. 38. Auriga. 5h.23m. N.35°45’. A grand cluster in a splendid neighbourhood.
M. 37. Auricmw. 5h.47m. N. 32°30’. An extremely beautiful cluster of about 500 stars.

M. 42 Ornronis. 5h. 31m. 8S. 5° 27’. “The Great Nebula in Orion,” visible to the naked eye, is a fine object ‘
even in small telescopes. In its brightest part are four stars of 6, 7, 7 4, and 8 mags., which form the well-
known “trapezium.” Two other stars have been glimpsed here in a 3-inch telescope.

H. VI. 33,34. 2h. 15m. N. 56° 45’. The Cluster in the Sword Handle of Perseus. Two magnificent clusters,
in the same field with a low power.

M.1 Tauri. 5h. 30m. N. 22° 0’. This nebula was discovered in 1731, forgotten, and rediscovered by Messier
in 1758. The discovery led him tc make his catalogue of 103 nebulw. The “Crab Nebula” of Lord Rosse.

Tue Prerapes. A beautiful naked-eye cluster of 6 or 7 stars, though some have made out 14, and even 16
without optical aid. Alcyone is the brightest star, 3rd mag. A very low power with a wide field should
be used.

MAPS 5 ann 6
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DOUBLE & MULTIPLE STARS.
h 273. Arcts. 7h. 35m. S. 26° 35’. A double star. Two 4th mag. stars at a distance of 10”.

5 Arcts. 7h. 44m. 8. 12°0'. A double star. The magnitudes of the components are 5} and 7}, and their
distance 3:3”,

€Cancrt. 8h. 7m. N. 17°50’. A triple star. Magnitudes 5, 54 and 53. Distances 1” and 5 5”.

a Canis Masoris (Sirius). 6h. 42m. 8S. 16° 35°. The brightest fixed star. Its 10th mag. companion is
invisible in all but the largest telescopes.

p Canis Masoris. 6h. 52m. 8. 13° 55’. A double star. Magnitudes 4:7 and 8. Distance 3”. Colours,
yellow and blue.

¢Geminorum. 6h. 59m. N. 20° 40’ The components of this star are of the 4th and 7th mags. Distance 94”.
Two faint comites have been seen, one of them with a 3 in. telescope.

6 Greminorum. 7h. 15m. N. 22°10’. A yellowish 3rd mag. star, with an 8th mag. companion, 7” distant.

a GEeMINORUM (Castor). Th. 29m. N. 32° 5’. A binary star with a period of about 1000 years. A splendid
object in a small telescope. Magnitudes 2} and 3}. Distance 6”.

17 Hyprz. 8h. 51m. 8. 7° 40’ Two almost equal stars of about the 7th mag., 4:3” apart.
12 Lyncrs. 6h. 39m. N. 59° 30’. A triple star. Magnitudes 5, 6 and 74. Distances 1:6” and 8-4”.

8 Monocerotis. 6h. 19m. N. 4° 40’. A double star in a grand low-power field. A yellow 4th mag. star,
with a bluish comes of between the 6th and 7th mag.

11 Monocrrotis. 6h. 25m. 8. 7° 0. A triple star. Magnitudes 5, 54 and 6. Distances 7” and 2-5”.

NEBULA & STAR CLUSTERS.
H. IV. 27. Hypre. 10h. 21m. 8.18° 15’. A planetary nebula south of p. It is of a slightly elliptical shape,
resembling Jupiter. It bears magnifying well.
H. VII. 2. Monocerotis. 6h. 28m. N. 4°55’. A beautiful cluster, the brightest stars being of the 7th and
8th magnitudes. It includes the 6th mag. star 12 Monocerotis,
M. 50 Monocerotis. 6h. 59m. 8. 8° 11’. A brilliant cluster.

M. 44 Cancrt. 8h. 35m. WN. 20° 15’. Praesepe. A naked-eye cluster. A large field and a low power are
needed to see it properly. :

M. 67 Cancri. 8h. 47m. N. 12° 5’. A loose cluster of about 200 stars, chiefly of the 9th and 10th magni-
tudes.

M. 35 Geminorum. 6h. 4m. WN, 24° 20°. A glorious cluster, visible to the naked eye.

MAPS 7 ann 8
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TELESCOPIC OBJECTS—MAPS 9 & 10.

DOUBLE STARS.
a (12) Canumw Venaticorum (Cor Caroli), 12h. 52m. N. 38° 45’. A double star. Magnitudes 3 and 6.
Distance 20”.

12 Com Brrenices. 12h.18m. N. 26°15’. A 44 mag. star attended by one of 84 mag. at a distance of 66”.

6 Corvi. 12h. 26m. 8. 16° 5’. A double star. The principal star is of the 3rd mag. and yellow. Magni-
tude of companion, 83. Distance 24”.

21669 Corvi. 12h. 387m. 8. 12° 35’. A pair of equal 64 mag. stars. Distance 5:4”.

a Leonts (Regulus). 10h. 4m. N. 12° 20’. Has a companion of the 8} mag., distant 177”. The comes is also
a double, but very difficult.

y Leonis. 10h. 15m. N, 20°15. A beautiful object. It consists of a 2nd mag. star with a 34 mag. com-
panion 3-6” distant (1907).

tLezovis. 11h. 20m. N. 11° 0. A binary star. Magnitudes 4 and 7. Distance 2:4” (1906).

& Urs Masoris, 11h. 14m. N. 32° 0’. A fine binary star, with a period of about 61 years. The magnitudes
of its components are 4 and 5, their distance 2°5” (1907).

y Vireinis. 12h. 37m. 8. 1° 0’ A very fine binary star, with a period of about 180 years. In 1780 the
distance of the components was 6”. In 1836 they could only be seen as an elongated star. Since then
they have gradually widened to 5-6" (1891). The stars are both of the 3rd magnitude.

6 Virernis. 13h. 6m. 8. 5° 5’. A 4th mag. star with a 9th mag. comes, 7” distant. A severe test for a 3 in.
telescope, though Ward glimpsed it with 2} in. in 1875.

VARIABLE STARS.
my Arcts. 10h. 42m. 8. 59°15’. A most remarkable variable star, in a wonderful nebula. In 1677 it was 4th
mag., rose to 2nd mag. in 1751, then sank to 4th mag. In 1827 it rose to lst mag. and for about five
years was 2nd mag. In 1837 it returned to lst mag., faded slightly, and then in 1843 became almost as
bright as Sirius. In 1862 it became invisible to the naked eye. It was 7th mag. in 1892 and 74 mag. in
1902.

NEBULE & STAR CLUSTERS.
M. 51 Canum Venaticorum, 13h. 26m. N. 47° 35’. A spiral nebula; but small telescopes will not show its
formation.
M. 3 Canum Venaticorum. 13h. 38m. N. 28° 45’. A beautiful globular cluster, but hardly resolvable into
stars with a small telescope.

MAPS 9 anv 10
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DOUBLE STARS.
« Booris. 14h. 11m. N. 52°10’. One of three stars near the end of the Great Bear’s tail. A 5th mag. star
with a 7th mag. attendant. Distance 12-6”.
a Boos. 14h. 37m. N. 16°45’. A double star. Magnitudes 5 and 6. Distance 7”.
¢ Bootis (Pulcherrima). 14h. 42m. N. 27° 15’. A beautiful double star, consisting of a 3rd mag. yellow, and

a 64 mag. blue star, at 2°6” distance. A most lovely object and a test for small instruments. It has been
well seen in 23-inch achromatic.

€ Boris. 14h. 48m. N. 19° 25’. A binary star. The magnitudes of its components are 4‘7 and 6:6.
Distance 3:2” (1891). The period is probably about 130 years.
¢ Corona Borgauis, 15h. 36m. N. 36°55’. A white 4th mag. star with a greenish 6th mag. companion 6”
distant.
a Hercuuis. 17h. 11m. N. 14° 30’. One of the first doubles in the heavens. A 3rd mag. variable orange
star with a blue or green attendant of the 6th mag., distant 4:6”.
36 Opuiucn1. 17h. 10m. 8. 26° 30’. A binary star. Two 6th mag. stars, 4°3” apart (1888).
39 OpHiucnt. 17h. 13m. 8S. 24° 10’... A beautiful double star. A 54 mag. orange star with a 6 mag. blue
companion at 15” distance.
&Scorpionis. 16h.0m. §.11° 10’. A triple star. The magnitudes of the components are 5,5,and 7. Their
distances in 1888 were 1” and 7”. In 1907 the nearer pair had closed up to 0:2”.
B Scorptonis. 16h. 1m. 8. 19° 35’. A double star. The magnitudes are 2 and 4, and their distance 13”.
a Scorpionis (Antares). 16h. 24m. 8. 26°15’. <A fiery red star of the first magnitude. It has a 7th mag. green
companion 3” distant; but this can rarely be seen in small telescopes, owing to the overpowering glare of
the large star.

$8 Serpentis. 15h. 3lm. N.10° 50’. A binary system. The components are of the 3rd and 4th mags. Dis-
tance 3°6” (1889).

VARIABLE STARS & STAR CLUSTERS.

T Coron# Borzauis. 15h. 56m. N. 26° 10’. The “Blaze Star” flamed up to 2nd mag. in 1866, and has
since decreased irregularly. 9th mag. in 1892.

M.13 Hercuus. 16h. 39m. N. 36° 35’. A grand cluster between 7» and ¢, and nearer the former. It is
visible to the naked eye.

M.19 Opniucu1. 16h. 57m. 8. 26° 10’. A bright cluster, but low for observation in the latitude of the
British Isles.

M. 9 OpHiucui. 17h. 14m. 8. 18° 25’. A small but brilliant cluster.
M. 23 Opatucui. 17h. 52m. 8.19° 0’. A splendid field with a low power.

MAPS 11 ann 12
(XIV hrs. to XVII hrs.)

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DOUBLE STARS.
¢Aquaru. 22h. 25m. S. 0° 25’. A beautiful object. Two 4th mag. stars at a distance of 3” (1892).
15 Aquitm, 19h. lm. 8. 4° 10. A double star. The components are of 6 and 74 mags., and their
colours yellow and ruddy. Distance 34”. About 1° N. of \ and slightly preceding it.
a Aquitm. 19h. 45m. N.11° 35’. A double star with components of the 6th and 7th mags. Distance 1-4”.
A test object for a 3 in. telescope.
a CapricorNi. 20h. 13m. 8. 12° 45’, A grand naked-eye pair. The stars are of the 3rd and 4th magritudes
and 6’ 16” apart.
B Cyenr, 19h. 27m. N, 27° 45’. A magnificent double star. A 3rd mag. golden-yellow star with a blue
attendant of 54 mag. Distance 34”.
61 Cyen1. 21h. 3m. N. 38° 20’. The first star to have its distance measured, by Bessel. A double star.
Magnitudes 54 and 6, nearly equal. Distance 21”.
p Cyenr. 21h. 40m. N, 28° 25’. A double star. Magnitudes 4.and 5. Distance 5-6”.
y Devrnini. 20h. 43m. N. 15° 50’. A beautiful and easy double star. The magnitudes are 4 and 5, and
their distance 11”.

a Lyre (Vega). 18h. 34m. N. 38° 40’. Is considered by some to be the second brightest fixed star. It has’
a 10th mag, attendant 52” off, which has been seen on rare occasions with smaller apertures, but is a hard
test for a 3 in. telescope. There are several distant small stars in the field.

e'and < Lyrw. 18h. 42m. N. 39° 30’. The ‘“Double-double.” The two stars have been seen by the naked eye
by several observers: to most they appear elongated. «1 has components of mags. 44 and 6} at 3” distance;
é of 5 and 5-2 mag. at 2:3” distance. Between the pairs are 3 other stars, one of them very faint.

NEBULA & STAR CLUSTERS.
M.2 Aquarn. 21h. 29m. S. 1°10". A magnificent globular cluster of 5’ or 6’ diameter.

M.11 Aquitz. 18h. 46m. S. 6° 20. A grand cluster, just visible to the naked eye,

M. 57 Lyre, 18h. 51m. N. 32° 55’. The “Ring Nebula,” between B and y. Its form may be seen in a 2h in.
telescope. It bears magnifying well.

M.20 Sacirrarnu. 17h. 57m. S. 23° 0°. The “Trifid Nebula.” In large telescopes, three dark rifts are seen
to meet in the middle of the nebula.

M.8 Sacrrrarm. 17h, 59m. §. 24°20. A splendid cluster. Fine low-power field.

M.27 VutrecuLrz. 19h. 56. N. 22° 30’. The “Dumb-bell Nebula,” so called from its appearance in
moderate-sized telescopes.

MAPS 13 anno 14
(XVII hrs. to XXI hrs.)

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DOUBLE STARS.
a CenTauRI. 14h. 34m. S. 60° 30’. The nearest fixed star. A remarkable binary star, with a period of 81
years, The finest in the heavens. It is composed of two yellow stars, lst and 2nd magnitudes, distant
16-5” in 1836, 7-6” in 1851, 18-6” in 1890, 21-6” in 1902.
a Crucis. 12h. 22m. S8. 62°40’. This magnificent object consists of two 2nd mag. stars, nearly 5” apart,
with a 6th mag. star at a distance of 90”.

y Crucis. 12h. 26m. 8. 56° 40’. A second mag. star with a 5th mag. comes at 101” distance. The brighter
star, of an orange-yellow colour, is probably variable.

pw Crucis, 12h. 50m. S. 56° 45’. A double star. The components are of the 5th and 6th magnitudes,
Distance 34”.

6 (p) Entpani. 1h. 37m. §. 56° 35’. Two 6th mag. stars 3-6” apart in 1835, 7” in 1890, forming a binary
system.

9367 Lac. Gruis, 23h. 3m. 8. 51° 5’. Adouble star. Magnitudes 64 and 7. Distance 8”.
d Ocrantis. 21h. 39m. 8S, 83°5’, A double star. Magnitudes 6 and 9. Distance 3:4”.
t Picroris. 4h. 49m. S. 53° 35’. A double star. Magnitudes 54 and 64. Distance 12”.

y Piscis Votantis. 7h. 9m. S. 70° 25’. A double star. The components are of the 4} and 7th mags.
Distance 13”.

2 Toucan. Oh. 52m. 8S. 70° 0’. A double star. The components are of the 7th and 8th mags. Distance 21”,

NEBULE & STAR CLUSTERS.
30 Dorapts. 5h. 39m. 8. 69°10’. A large, bright nebula “in the form of a loop.”

265 A Canine. 9h. 10m. S. 64° 30’. A large, rich, globular cluster.
« Crucis. 12h. 49m. S. 59° 55’. Is surrounded by a bright and beautiful cluster of stars of various colours.

47 Toucan. Oh. 20m. 8. 72° 30’. A grand globular cluster, containing about 1500 stars of the 12th to
14th magnitude. Visible to the naked eye as a hazy 4} mag. star. ‘A superb object” (Sir J. Herschel).

MAPS 15 ann 16
(Circumpolar, South )

MAP I5

ANNO 1920.

ABBREVIATIONS
Greek letter (to a star,) Bayer's designation.
Small Roman letter ,, % Pa
» Capitals R to Z (toa star,) Variable stars,
Number only (toa star.) | Flamsteed’s number.
* (to neb.,) Sir J. Herschel's No. (New Ed)
Number underlined (to a star,) Piazzi’s No.
Number with small no.) Sir W. Herschel’s
to right of it. (to reba number and class.

B.A.C. British Association number.
fp Burnham's number.
Br. Brisbane's number.

& ‘Dunlop's number.

E-B_ Espin and Birmingham's number.
H Sir W. Herschel's number.
h Sir J. Herschel’s number.
Jac. Jacob's number.

Lac. Lacaille's number.

LI. Lalande's number.

M_ Messier’s nebule number.
OZ Otto Struve's number.
OLE Pulkowa Cat, Pt. Il. No,

R or Ru. (small, to star)

= Ruddy or yellow star.

Rus. Russell's number.

Sa. Santiago number.

St. Stone’s number.

= sSF. Struve’s number.

2 Do, App'dix I. do.

V or Var. (small, to star)

= Variable star.

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INDEX TO THE CONSTELLATIONS.

With the number of the Map in which each is shown, and the approximate date of culmination of

For each Hour later or earlier than 9 a.m. or midnight—

Earlier—Add 15 days to dates given below.
Later—Subtract 15 days from _,,

”

its central hour of Right Ascension at 9 p.m. and Midnight.

For each Week later or earlier than dates below—
Earlier—Add 28 minutes to 9 p.m. or midnight.
» from

Later—Subtract

”

”

Name of Constellation. Bee Mop Guleteation Gaiieeton Name of Constellation. sep Gugieanoe ‘Chininstion
: 9 p.m. Midnight. 7 9 p.m. Midnight.
ANDROMEDA 8 | Nov. 15 | Oct. 1 || Inpust .|14, 15] Sept. 26 | Aug. 12
Antirat .., 8 | Apr. 10 | Feb. 24 || Lacerrat 8 | Oct. 14} Aug. 30
Apust 16 | June 30 | May 16 || Lzo aes 9 | Apr. 15 | Mar. 1
AQUARIUS 4 | Oct. 7 | Aug. 23 || Leo Mrnort 9 | Apr. 12 | Feb. 26
AQUILA 13 | Aug. 30 | July 16 | Lepus 6 | Jan. 29 | Dec. 15
ARA 12 | July 22) June 7 || Lrera 12 | June 25 / May 11
ARGO 8 | Mar. 11] Jan. 25 |) Lupus 12 | June 19 |} May 5
ARIES 5 | Dec. 12 | Oct. 28 |] Lynxt 1,7 | Mar. 5 | Jan. 19
AURIGA 5 | Feb. 2 | Dec. 19 || Lyra sf 13 | Aug. 18/ July 4
Boorss 11 | June 12} Apr. 28 || Matust (Argo) ... 8 | Mar. 19] Feb. 2
Cartumt ... 6 | Jan. 13 | Nov. 29 |] Mensat . 15, 16] Feb. 3 | Dec. 20
CaMELOPARDUSt ... 1,2 | Jan. 31 | Dec. 17 || Microscoriumt ... 14 | Sept. 19) Aug. 5
CaNcER a 7 =| Mar. 12 | Jan. 26 || Monocrrost 7,8 | Feb, 22) Jan. 8
Canes Venatici t 9 | May 21 | Apr. 6 || Muscat 16 May 14] Mar. 30
Canis Masor 8 | Feb. 13 | Dec. 30 }} Normat 12 | July 6] May 22
Canis Minor 7 =| Feb. 27 | Jan. 13 |] Ocranst ... 15, 16 Cireum|polar
CaPRICORNUS 14 | Sept. 19 | Aug. 5 || Oparucuus 11,12] July 25} June 10
Carina t (ARGO) a 8, 16 | Mar. 16 | Jan. 30 || Onton 5, 6 Jan. 23 | Dec. 9
CASSIOPEIA 2,3 | Nov. 20 | Oct. 6 |] Pavot 15 | Aug. 24 | July 10
CENTAURUS 10 | May 25 | Apr. 10 || Pecasus ... 3 | Oct. 15 | Aug. 31
CEPHEUS ... 2 | Oct. 10] Aug. 26 |] Perseus. ... 5 Dec. 21} Nov. 6
Crrus 4,5 | Nov. 30 | Oct. 16 || Pooznrxt 4 ; Nov. 9, Sept. 25
CHAMAELEON t 16 Apr. 13 | Feb. 27 || Picrort 6 Jan. 29 | Dec. 15
Crrcinus t ; 12, 16) June 24 | May 10 || Pisces sist 8 | Nov. 12 | Sept. 28
Corium t (CarLum) 6 | Jan. 13 | Nov. 29 |] Prscis AusrRauis 4 | Sept. 30 | Aug. 16
Cotumpa t 6 | Jan. 31] Dec. 17 || Pupprst (Arco) ... 8 | Feb. 26 | Jan. 12
Coma Berenices t Q9 | May 17 | Apr. 2 | Reticutumt 15 | Jan. 41] Nov. 20
Corotia (Corona Australis) : SAGITTA 13 Aug. 31 | July 17
Corona AUSTRALIS : } Ae) (ears te | ae SaGITTaRius 14 pene 20 | J ee 6
Corona BoREALIS 11 | July 2) May 18 || Scorpio 12 | July 10}; May 26
Corvus 10 | May 13] Mar. 29 || Scunprort 4 | Nov. 14 | Sept. 30
CRATER 10 | Apr. 28 | Mar. 14 |] (Scurum t)* 13 | Aug. 12 | June 28
Crux t 16 May 14] Mar. 30 ||Srrpens ... 11 July 21 | June 6
Cyanus 13 | Sept. 10 | July 27 || Szxranst... 9,10) Apr. 9/| Feb. 23
DELPHINUS 13 | Sept. 15 | Ang. IL || Taurus “ee is 5 | Jan. 15] Dec. 1
Dorapot... 15, 16] Jan. 17 | Dec. 3 || (Tavrus Pontatowsk1) 18 | Aug. 9 | June 25
Draco 1,2 | July 10) May 26 |] Texescorrumt 14 | Aug. 14 | June 30
EQuuLeus 13 Sept. 21; Aug. 7 }) Toucant : # 15 Oct. 30 | Sept. 15
Eripanvs... 6 | Jan. 2] Nov. 18 || Trrancutum AustTRaet 16 | July 4); May 20
Fornaxt ... 6 | Dec. 12 | Oct. 28 || Trrancutum 3 | Dec. 5 | Oct, 21
GEMINI 7 =| Feb. 20) Jan. 6 || Ursa Mason 1,9 | Apr. 21] Mar. 7
Grus t 4 | Oct. 9 | Aug. 25 || Ursa Minor 1 | June 25 | May 11
HERCULES ie «| 44° | July 21) June 6 || Verat (Arco) 8 | Mar. 29 | Feb. 12
Horotoerum t 6,15 | Dec. 20! Nov. 5 ]|/ Virco... oe «| 9,10} May 25 | Apr. 10
Hypra 7,10 | Apr. 30 | Mar. 16 || Vouayst ... ais 16 | Mar. 1/ Jan. 15
Hyprust... 15 | Dec. 14 | Oct. 30 || Vutpecurat 13 | Sept. 8 | July 25

* This constellation (Scutum Sobieskii) is occasionally used, especially in America, to denote the lower corner of Aquila adjoining the tail of

Serpens.

Aquile; €=3 Aquila; 17=9 Aquile.

It extends from about R.A. 18h, to 18h. d6m., and from Dec. 2° S. to 16° 8. 5 : y :
+ Taurus PonIATOWSKII is another small modern asterism. It is situated in the region bordering Hercules,

a=1 Aquilz ;

between Aquila and Ophiuchus, where some stars form the letter V. Constellations so marked are modern.

B=6 Aquile; y=B.A.C, 6279; d=2

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