The following is a list of the Lunar Formations numbered as on the Key-map, Plate [XIX].:
In the accompanying brief notes on a few important formations, the diameter of each is given in miles, and the height of the highest peak on wall in feet. The day of each lunation on which it may be well seen is also added.
NO.
22. Maginus.—Great walled plain; 100 miles; 14,000 feet. Central mountain 2,000 feet. Difficult in full, owing to rays from Tycho. Plate [XIV.] Eighth and ninth days.
23. Longomontanus.—Walled plain; 90 miles; 13,314 feet. Crossed by rays from Tycho. Plate [XV.] Ninth day.
26. Wargentin; 28. Schickard.—Close together. 26. Curious ring plain; 54 miles. Seemingly filled with lava. 'Resembles a large thin cheese.' 28. Great walled plain; 134 miles; 9,000 feet. Floor 13,000 square miles area, very varied in colour. Walls would be invisible to spectator in centre of enclosure. Plate [XII.] Thirteenth and fourteenth days.
30. Tycho.—Splendid ring plain; 54 miles; 17,000 feet. Central mountain 5,000 feet. Great system of streaks from neighbourhood. Plates [XII.], [XIII.], [XV.] Ninth and tenth days.
32. Stöfler.—Walled plain. Peak on N.E. wall 12,000 feet. Floor very level. Beautiful steel-grey colour. Plate [XVI.] Seventh day.
33. Maurolycus.—Walled plain; 150 miles; 14,000 feet. In area equal to about half of Ireland. Floor in full covered with bright streaks. Plate [XVI.] Seventh day.
58. Piccolomini.—Ring plain; 57 miles; 15,000 feet on E. Fine central mountain. Very rugged neighbourhood. Plate [XI.] Fifth and sixth days.
63. Pitatus.—58 miles. Wall massive on S., but breached on N. side, facing Mare Nubium. Two clefts in interior shown Plate [XV.] Ninth day.
78. Fracastorius.—Another partially destroyed formation; 60 miles. Wall breached on N., facing Mare Nectaris. Under low sun traces of wall can be seen. Plate [XI.] Fifth and sixth days.
80. Petavius.—Fine object; 100 miles; 11,000 feet. Fine central peak 6,000 feet. Great cleft from central mountain to S.E. wall can be seen with 2-inch. Third and fourth days, but best seen on waning moon a day or two after full.
90. Gassendi.—Walled plain; 55 miles. Wall on N. broken by intrusive ring-plain of Gassendi A. Fine central mountain 4,000 feet. Between thirty and forty clefts in floor, more or less difficult. Plates [XII.], [XIII.] Eleventh and twelfth days.
95. Catherina; 96. Cyrillus; 97. Theophilus.—Fine group of three great walled plains. 95. Very irregular; 70 miles; 16,000 feet. Connected by rough valley with 96. 96 has outline approaching a square; walls much terraced, overlapped by 97, and partially ruined on N.E. side. 97 is one of the finest objects on moon; 64 miles; terraced wall, 18,000 feet. Fine central mountain 6,000 feet. Plates [XI.], [XVI.] Sixth day.
84. Arzachel; 110. Alphonsus; 111. Ptolemæus.—Another fine group. 84 is southernmost; 66 miles; 13,000 feet. Fine central mountain. 110. Walled plain; 83 miles; abutting on 111. Wall rises to 7,000 feet. Bright central peak. Three peculiar dark patches on floor, best seen towards full. 111 is largest of three; 115 miles. Many large saucer-shaped hollows on floor under low sun. Area 9,000 square miles. Plate [XIII.] Eighth and ninth days.
125. Grimaldi.—Darkest walled plain on moon; 148 miles by 129; area 14,000 square miles; 9,000 feet. Plate XII. Thirteenth and fourteenth days.
131. Messier and Messier A.—Two bright craters; 9 miles. Change suspected in relative sizes. From Messier A two straight light rays like comet's tail extend across Mare Fœcunditatis. Fourth and fifth days.
147. Copernicus.—Grand object; 56 miles; 10,000 to 12,000 feet. Central mountain 2,400 feet. Centre of system of bright rays. On W. a remarkable crater row; good test for definition. Plates [XII.], [XIII.] Ninth and tenth days.
150. Triesnecker.—Small ring plain; 14 miles. Terraced wall 5,000 feet. Remarkable cleft-system on W. Rather delicate for small telescopes. Plate [XIII.] Seventh and eighth days.
158. Hyginus.—Crater-pit 3·7 miles. Remarkable cleft runs through it; visible with 2-inch: connected with Ariadæus rill to W., which also an object for a 2-inch. Dark spot to N.W. on Mare Vaporum named Hyginus N. Has been suspected to be new formation. Plate [XII.] Seventh day.
168. Eratosthenes.—Fine ring plain at end of Apennines; 38 miles. Terraced wall 16,000 feet above interior, which is 8,000 feet below Mare Imbrium. Fine central mountain. Plate [XIII.] Remarkable contrast to 148 Stadius, which has wall only 200 feet, with numbers of craters on floor. Ninth and tenth days.
175. Herodotus; 176. Aristarchus.—Interesting pair. 175 is 23 miles; 4,000 feet. Floor very dusky. Great serpentine valley; most interesting object. Easy with 2-inch. 176 is most brilliant crater on moon; 28 miles; 6,000 feet. Central peak very bright. Readily seen on dark part of moon by earth-shine. Plates [XII.], [XIII.] Twelfth day.
188. Linné.—Small crater on M. Serenitatis near N.W. end of Apennines. Suspected of change, but varies much in appearance under different lights. Visible on Plate [XVII.] as whitish oval patch to left of end of Apennines. Seventh day.
191. Archimedes.—Fifty miles; 7,000 feet. Floor very flat; crossed by alternate bright and dark zones. Makes with 189 and 190 fine group well shown Plate [XVII.] Eighth day.
208. Eudoxus; 209. Aristoteles.—Beautiful pair of ring plains. 208 is 40 miles. Walls much terraced; 10,000 to 11,000 feet; 209 is 60 miles; 11,000 feet. Plate [XVII.] Sixth and seventh days.
210. Plato.—Great walled plain; 60 miles; 7,400 feet. Dark grey floor, which exhibits curious changes of colour under different lights, also spots and streaks too difficult for small telescope. Landslip on E. side. Shadows very fine at sunrise. Plates [XII.], [XIII.] Ninth day.
211. Pico.—Isolated mountain; 7,000 to 8,000 feet. S. of 210. Casts fine shadow when near terminator. Ninth and tenth days.
228. Atlas; 229. Hercules.—Beautiful pair. 228 is 55 miles; 11,000 feet. Small but distinct central mountain. 229 is 46 miles. Wall reaches same height as 228, and is finely terraced. Landslip on N. wall. Conspicuous crater on floor. Plate [XI.] Fifth day.
APPENDIX II
The following list includes a number of double and multiple stars, clusters, and nebulæ, which may be fairly well seen with instruments up to 3 inches in aperture. A few objects have been added on account of their intrinsic interest, which may prove pretty severe tests. The places given are for 1900, and the position-angles and distances are mainly derived from Mr. Lewis's revision of Struve's 'Mensuræ Micrometricæ,' Royal Astronomical Society's Memoirs, vol. lvi., 1906. For finding the various objects, Proctor's larger Star Atlas, though constructed for 1880, is still, perhaps, the most generally useful. Cottam's 'Charts of the Constellations' (Epoch 1890) are capital, but somewhat expensive. A smaller set of charts will be found in Ball's 'Popular Guide to the Heavens,' while Peck has also published various useful charts. The student who wishes fuller information than that contained in the brief notes given below should turn to Gore's exceedingly handy volume, 'The Stellar Heavens.'
The brighter stars are generally known by the letters of the Greek alphabet, prefixed to them by Bayer. When these are used up, recourse is had either to the numbers in Flamsteed's Catalogue, or to those in Struve's 'Mensuræ Micrometricæ.' The Struve numbers are preceded by the Greek Σ. A few of the more notable variable and red stars are included; these are generally marked by capital letters, as V. AQUILÆ. The order of the notes is as follows. First is given the star's designation, then its place in hours and minutes of right ascension and degrees and minutes of declination, N. and S. being marked respectively by + and −; then follow the magnitudes; the position-angles, which are measured in degrees from the north, or bottom point of the field, round by east, south, and west to north again; the distances of the components from one another in seconds of arc; and, finally, short notes as to colour, etc. According to Dawes, one inch aperture should separate the components of a 4·56″ double star, two inches those of a 2·28″, three those of a 1·52″, and so on. If the observer's glass can do this on good nights there is little fault to find with it. Double stars may be difficult for other reasons than the closeness of the components; thus, a faint companion to a bright star is more difficult to detect than a companion which is not far below its primary in brightness. Clusters and nebulæ, with a few exceptions, are apt to prove more or less disappointing in small instruments. The letters of the Greek alphabet are as follows:
| α Alpha. | η Eta. | ν Nu. | τ Tau. |
| β Beta. | θ Theta. | ξ Xi. | υ Upsilon. |
| γ Gamma. | ι Iota. | ο Omicron. | φ Phi. |
| δ Delta. | κ Kappa. | π Pi. | χ Chi. |
| ε Epsilon. | λ Lambda. | ρ Rho. | ψ Psi. |
| ζ Zeta. | μ Mu. | σ Sigma. | ω Omega. |
Andromeda.
M. 31: 0 h. 37 m. + 40° 43′. Great Spiral Nebula. Visible to naked eye near ν Andromedæ. Rather disappointing in small glass.
Σ 205 or γ : 1 h. 58 m. + 41° 51′ : 3-5 : 62′5° : 10·2″. Yellow, bluish-green. 5 is also double, a binary, but a very difficult object at present.
Aquarius.
M. 2 : 21 h. 28 m. − 1° 16′. Globular cluster; forms flat triangle with α and β.
Σ 2909 or ζ : 22 h. 24 m. − 0° 32′ : 4-4·1 : 319·1° : 3·29″. Yellow, pale yellow. Binary.
Aquila.
M. 11 : 18 h. 46 m. − 6° 23′. Fine fan-shaped cluster. Just visible to naked eye.
V : 18 h. 59 m. − 5° 50′. Red star, variable from 6·5 to 8·0.
Argo Navis.
M. 46 : 7 h. 37 m. − 14° 35′. Cluster of small stars, about ½° in diameter.
Aries.
Σ 180 or γ : 1 h. 48 m. + 18° 49′ : 4·2-4·4 : 359·4° : 8·02″. Both white. Easy and pretty.
λ 1 h. 52 m. + 23° 7′ : 4·7-6·7 : 47° : 36·5″. Yellow, pointed to by γ and β.
Auriga.
(Capella) α : 5 h. 9 m. + 45° 54′. Spectroscopic binary; period 104 days.
M. 37 : 5 h. 46 m. + 32° 31′. Fine cluster. M. 36 and M. 38 also fine. All easily found close to straight line drawn from κ to φ Aurigæ.
β : 5 h. 52 m. + 44° 57′. Spectroscopic binary, period 3·98 days.
41: 6 h. 4 m. + 48° 44′ : 5·2-6·4 : 353·7 : 7·90″. Yellowish-white, bluish-white.
Boötes.
Σ 1864 or π : 14 h. 36 m. + 16° 51′ : 4·9-6 : 103·3° : 5·83″. Both white.
Σ 1877 or ε : 14 h. 40 m. + 27° 30′ : 3-6·3 : 326·4° : 2·86″. Yellow, blue. Fine object and good test.
Σ 1888 or ξ : 14 h. 47 m. + 19° 31′ : 4·5-6·5 : 180·4° : 2·70″. Yellow, purple, binary.
Σ 1909 or 44 : 15 h. 0 m. + 48° 2′ : 5·2-6·1 : 242° : 4·32″.
Camelopardus.
V. : 3 h. 33 m. + 62° 19′. Variable, 7·3 to 8·8. Fiery red.
Cancer.
Σ 1196 or ζ : 8 h. 6 m. + 17° 57′ : 5-5·7-6·5 : 349·1°, 109·6° : 1·14″, 5·51″. Triple ; 5 and 5·7 binary, period 60 years; 6·5 revolves round centre of gravity of all in opposite direction.
Σ 1268 or ι : 8 h. 41 m. + 29° 7′ : 4·4-6·5 : 307° : 30·59″. Yellow, blue.
Præsepe: Cluster, too widely scattered for anything but lowest powers.
Canes Venatici.
Σ 1622 or 2 : 12 h. 11 m. + 41° 13′ : 5-7·8 : 258° : 11·4″. Gold, blue.
Σ 1645 : 12 h. 23 m. + 45° 21′ : 7-7·5 : 160·5° : 10·42″. White. Pretty, though faint.
Σ 1692, 12, or α : 12 h. 51 m. + 38° 52′ : 3·1-5·7 : 227° : 19·69″. Cor Caroli. White, violet.
M. 51 : 13 h. 26 m. + 47° 43′. Great spiral. 3° S.W. of η Ursæ Majoris.
M. 3 : 13 h. 38 m. + 28° 53′. Fine globular cluster; on line between Cor Caroli and Arcturus, rather nearer the latter.
Canis Major.
M. 41 : 6 h. 43 m. − 20° 38′. Fine cluster, visible to naked eye, 4° below Sirius.
Canis Minor.
(Procyon) α : 7 h. 34 m. + 5° 30′ : 0·5-14 : 5° 4·46″. Binary, companion discovered, Lick, 1896, only visible in great instruments.
Capricornus.
α : 20 h. 12 m. − 12° 50′ : 3·2-4·2. Naked eye double, both yellow.
M. 30 : 21 h. 35 m. − 23° 38′. Fairly bright cluster.
Cassiopeia.
Σ 60 or η : 0 h. 43 m. + 57° 18′ : 4-7 : 227·8° : 5·64″. Binary; period about 200 years.
Σ 262 or ι : 2 h. 21 m. + 66° 58′ : 4·2-7·1-7·5 : 250°, 112·6° : 1·93″, 7·48″. Triple.
H. vi. 30 : 23 h. 52 m. + 56° 9′. Large cloud of small stars.
Σ 3049 or σ : 23 h. 54 m. + 55° 12′ : 5-7·5 : 325·9° : 3·05″. Pretty double, white, blue.
Cepheus.
κ : 20 h. 12 m. + 77° 25′ : 4-8 : 123° : 7·37″. Yellowish-green.
Σ 2806 or β : 21 h. 27 m. + 70° 7′ : 3-8 : 250·6° : 13·44″. White, blue.
S : 21 h. 36 m. + 78° 10′. Variable, 7·4 to 12·3. Very deep red.
Σ 2863 or ξ : 22 h. 1 m. + 64° 8′ : 4·7-6·5 : 283·3°: 6·87″. Yellow, blue.
δ : 22 h. 25 m. + 57° 54′ : variable-5·3 : 192° : 40″. Yellow, blue. Primary varies from 3·7 to 4·9. Period, 5·3 days. Spectroscopic binary.
Σ 3001 or ο : 23 h. 14 m. + 67° 34′ : 5·2-7·8 : 197·3° : 2·97″. Yellow, yellowish-green.
Cetus.
(Mira) ο : 2 h. 14 m. − 3° 26′. Variable. Period about 331 days. Maxima, 1·7 to 5; minima, 8 to 9. Colour, deep yellow to deep orange.
Σ 281 or ν : 2 h. 31 m. + 5° 10′ : 5-9·4 : 83·1°: 7·74″. Yellow, ashy.
Σ 299 or γ : 2 h. 38 m. + 2° 49′ : 3-6·8 : 291° : 3·11″. Yellow, blue, slow binary.
Coma Berenices.
Σ 1657 or 24 : 12 h. 30 m. + 18° 56′ : 5·5-7 : 271·1° : 20·23″. Orange, blue.
M. 53 : 13 h. 8 m. + 18° 42′. Cluster of faint stars.
Corona Borealis.
Σ 1965 or ζ : 15 h. 36 m. + 36° 58′ : 4·1-5 : 304·3° : 6·15″. White greenish.
R : 15 h. 44 m. + 28° 28′. Irregularly variable, 5·5 to 10·1.
Σ 2032 or σ : 16 h. 11 m. + 34° 6′ : 5-6·1 : 216·3° : 4·80″. Yellow, bluish. Binary, period about 400 years.
Corvus.
δ : 12 h. 25 m. − 15° 57′ : 3-8·5 : 214° : 24·3″. Yellow, lilac.
Crater.
R. : 10 h. 56 m. − 17° 47′. Variable. About 8 magnitude. Almost blood-colour.
Cygnus.
Σ 2486 : 19 h. 9 m. + 49° 39′ : 6-6·5 : 218·2° : 9·63″. 'Singular and beautiful field' (Webb).
(Albireo) β : 19 h. 27 m. + 27° 45′ : 3-5·3 : 55° : 34·2″. Orange-yellow, blue. Easy and beautiful.
Σ 2580 or χ : 19 h. 43 m. + 33° 30′ : 4·5-8·1 : 71·6° : 25·50″. 4·5 is variable to 13·5. Period 406 days.
Z : 19 h. 58 m. + 49° 45′. Variable, 7·1 to 12. Deep red.
RS : 20 h. 10 m. + 38° 27′. Variable, 6 to 10. Deep red.
U : 20 h. 16 m. + 47° 35′. Variable, 7 to 11·6. Very red.
V : 20 h. 38 m. + 47° 47′. Variable, 6·8 to 13·5. Very red.
Σ 2758 or 61 : 21 h. 2 m. + 38° 13′ : 5·3-5·9 : 126·8° : 22·52″. First star whose distance was measured.
RV : 21 h. 39 m. + 37° 33′. Variable, 7·1 to 9·3. Splendid red.
Σ 2822 or μ : 21 h. 40 m. + 28° 18′ : 4-5 : 122·2° : 2·29″. Fine double; probably binary.
Delphinus.
Σ 2727 or γ : 20 h. 42 m. + 15° 46′ : 4-5 : 269·8° : 10·99″. Yellow, bluish-green.
V : 20 h. 43 m. + 18° 58′. Variable, 7·3 to 17·3. Period 540 days. Widest range of magnitude known.
Draco.
Σ 2078 or 17 : 16 h. 34 m. + 53° 8′ : 5-6 : 109·5° : 3·48″. White.
Σ 2130 or μ : 17 h. 3 m. + 54° 37′ : 5-5·2 : 144·2° : 2·17″. White.
H. iv. 37 : 17 h. 59 m. + 66° 38′. Planetary nebula, nearly half-way between Polaris and γ Draconis. Gaseous; first nebula discovered to be so.
Σ 2323 or 39: 18 h. 22 m. + 58° 45′ : 4·7-7·7-7·1 : 358·2°, 20·8° : 3·68″, 88·8″. Triple.
ε : 19 h. 48 m. + 70° 1′ : 4-7·6 : 7·5° : 2·84″. Yellow, blue.
Equuleus.
Σ 2737 or ε : 20 h. 54 m. + 3° 55′ : 5·7-6·2-7·1 : 285·9°, 73·8° : 0·53″, 10·43″. Triple with large instruments.
Eridanus.
Σ 518 or 40 or 0^2 : 4 h. 11 m. − 7° 47′ : 4-9-10·8 : 106·3°, 73·6° : 82·4″, 2·39″. Triple, close pair binary.
Gemini.
M. 35 : 6 h. 3 m. + 24° 21′. Magnificent cluster; forms obtuse triangle with μ and η.
Σ 982 or 38 : 6 h. 49 m. + 13° 19′ : 5·4-7·7 : 159·7° : 6·63″. Yellow, blue. Probably binary.
ζ : 6 h. 58 m. + 20° 43′. Variable, 3·8 to 4·3. Period 10·2 days. Non-eclipsing binary.
Σ 1066 or δ : 7 h. 14 m. + 22° 10′ : 3·2-8·2 : 207·3° : 6·72″. Pale yellow, reddish.
(Castor) α : 7 h. 28 m + 32° 7′ : 2-2·8 : 224·3° : 5·68″. White, yellowish-green. Finest double in Northern Hemisphere.
Hercules.
M. 13 : 16 h. 38 m. + 36° 37′. Great globular cluster, two-thirds of way from ζ to η.
Σ 2140 or α : 17 h. 10 m. + 14° 30′ : 3-6·1 : 113·6° : 4·78″. Orange-yellow, bluish-green. Fine object.
Σ 2161 or ρ : 17 h. 20 m. + 37° 14′ : 4-5·1 : 314·4° : 3·80″. 'Gem of a beautiful coronet' (Webb).
M. 92 : 17 h. 14 m. + 43° 15′. Globular cluster; fainter than M. 13.
Σ 2264 or 95 : 17 h. 57 m. + 21° 36′ : 4·9-4·9 : 259·7° : 6·44″. 'Apple-green, cherry-red' (Smyth), but now both pale yellow.
Σ 2280 or 100 : 18 h. 4 m. + 26° 5′ : 5·9-5·9 : 181·7° : 13·87″. Greenish-white.
Hydra.
Σ 1273 or ε : 8 h. 41 m. + 6° 48′ : 3·8-7·7 : 231·6° : 3·33″. The brighter star is itself a close double.
V : 10 h. 47 m. − 20° 43′. Variable, 6·7 to 9·5. Copper-red.
W : 13 h. 44 m. − 27° 52′. Variable, 6·7 to 8·0. Deep red.
Lacerta.
Leo.
Σ 1424 or γ : 10 h. 14 m. + 20° 21′ : 2-3·5 : 116·5° : 3·70″. Fine double, yellow, greenish-yellow.
Σ 1487 or 54 : 10 h. 50 m. + 25° 17′ : 5-7 : 107·5° : 6·38″. Greenish-white, blue.
Σ 1536 or ι : 11 h. 19 m. + 11° 5′ : 3·9-7·1 : 55·0° : 2·36″. Yellow, blue.
Leo Minor.
Lepus.
R : 4 h. 55 m. − 14° 57′. Variable, 6·7 to 8·5. Intense crimson.
Libra.
M. 5 : 15 h. 13 m. + 2° 27′. Globular cluster, close to star 5 Serpentis. Remarkable for high ratio of variables in it—1 in 11.
Lynx.
Σ 948 or 12 : 6 h. 37 m. + 59° 33′ : 5·2-6·1-7·4 : 116°, 305·8° : 1·41″, 8·23″. Triple, greenish, white, bluish.
Σ 1334 or 38 : 9 h. 13 m. + 37° 14′ : 4-6·7 : 235·6° : 2·88″. White blue.
Lyra.
T : 18 h. 29 m. + 36° 55′. Variable, 7·2 to 7·8. Crimson.
(Vega) α : 18 h. 34 m. + 38° 41′ : 1-10·5 : 160° : 50·77″. Very pale blue. The faint companion is a good test for small telescopes. Vega is near the apex of the solar way.