These are mainly summer groups, though the northernmost parts of Hercules and Bootes are circumpolar in England. Rough times of rising and setting for Antares, in Scorpio, are as follows:
January 1st Rises 5 a.m., highest in daylight, sets in daylight. April 1st Rises 11 p.m., highest 3 a.m., sets in daylight.
July 1st Rises in daylight, highest in daylight, sets 1 a.m.
October 1st Rises in daylight, highest in daylight, sets in daylight.
Arcturus in Bootes is easily recognized, and is shown on Key Map I. Corona is also most conspicuous and can hardly be mistaken. The other groups are less easy to identify, as they are of large area but contain few bright stars. Scorpio is of course an exception, but the most brilliant part of the constellation is always very low in England.
BOOTES. The chief star is Arcturs; others are Epsilon (2.4), Eta (2.7), Gamma (3.0), and Delta and Beta (3.5). Arcturus is of type K and is distinctly orange.
Double Stars. Epsilon: magnitudes 2.5, 5.3; distance 3", P.A. 340°. the primary is yellowish, the companion bluish.
Zeta: magnitudes 4.6,4.7; distance about 1".3, P.A. 135°. This is close and rather difficult. Binary, period 123 years.
Xi: magnitudes 4.8,6.9; distance 7".0, P.A. 344°. Binary, period 152 years.
Delta: magnitudes 3.5,7.8; distance 105", P.A. 080°. A very easy object in a small telescope.
Variables. W and R, which lie close to Epsilon. R varies from magnitude 6 to 13 in 225 days; W from 5.2 to 6, irregular.
CORONA BOREALIS. This beautiful little constellation can hardly be mistaken, and it really does look rather like a "crown". The chief stars are Alpha (2.2) and Beta (3.7). Despite its small size, Corona is rich in interesting objects.
Double Stars. Eta: magnitudes 5.7,5.9; distance 1", P.A. varies rather quickly, as the star is a binary with a period of 42 years. It is rather close, and is thus not an easy object.
Zeta: magnitudes 4.0,4.9; distance 6".3, P.A. 303°. A fine double.
Variables. T: the peculiar nova-like variable. Usually it fluctuates between magnitudes 9 and 10, but it rose to 2 in 1866 and to 3 in 1946. It is well worth watching, as a fresh outburst may occur at any moment.
R: magnitude 5.6 to 14. The well-known irregular variable, described in the text.
S: magnitude 6 to 12, period 361 days. Spectrum M.
HERCULES. A very large but rather barren constellation. It occupies the area between Vega and Corona Borealis. The chief stars are Beta and Zeta (2.8), Alpha (variable), Pi and Delta (3.1), Mu (3.4), and Eta (3.5).
Double Stars. Zeta: magnitudes 3.1, 5.6; distance about 1". P.A. alters fairly quickly, as the star is a binary with a period of 34 years.
Delta: magnitudes 3.2,7.5; distance 11", P.A. 208°.
Alpha: magnitudes 3 (variable), 5.4; distance 4".6, P.A. 110°. The brighter star is an M5-type giant, reddish; the companion green.
Variables. Alpha. One of the Betelgeux-type irregulars. It fluctuates between magnitudes 3 and 4, and over about 20 years I have found no semblance of a period. The best comparison stars for it are Kappa Ophiuchi (3.42), Gamma Herculis (3.79), and Delta Herculis (3.14).
g: magnitude 4.6 to 6.0. An M-type irregular, near Sigma (4.2).
S: magnitude 6 to 12.5, period 300 days. Spectrum M. It lies between Alpha Herculis and Beta Serpentis.
Clusters. M.13. The famous globular; it lies between Zeta and Eta, and can just be seen with the naked eye under good conditions. It is very easy to find with a telescope, and in a moderate aperture is a glorious sight.
M.92: another globular, between Iota and Eta. It is not unlike M.13, but is far less prominent.
NGC 210 a small bright planetary nebula in the triangle formed by Beta, Delta, and Epsilon Herculis. It is said to have a bluish hue, though to me it always looks white.
OPHIUCHUS. This constellation lies between Vega and Antares. It contains some fairly bright stars: Alpha (2.1), Eta (2.5), Zeta (2.6), Delta (2.7), Beta (2.8), Kappa and Epsilon (3.2), and Mu and Nu (3.3), but it is not easy to identify at first sight, and it is relatively barren of interesting objects. There is a bright globular cluster, M.19, near Theta, and roughly between Theta and Antares; but it is always very low in England. Ophiuchus is not classed as a Zodiacal constellation, but it does enter the Zodiac in the region between Scorpius and Sagittarius.
LIBRA. Zodiacal, but a very dull constellation. The chief stars are Beta (2.6), Alpha (2.8), and Sigma (3.3); Sigma was also included in Scorpius, as Gamma Scorpii. There are few interesting objects apart from the Algol-type eclipsing binary Delta Librae, which has a magnitude range of 4.8 to 6.2 and a period of
2.3 days. Beta Librae is a B8-type star and is said to be the nearest approach to a normal "green" star. It certainly may have a slightly greenish tinge, though the colour is so elusive that many people will fail to detect it. Of course, some double stars have green components, and Nova DQ Herculis was also green at one stage in its career.
SCORPIUS. A splendid Zodiacal group, but never well seen in England; it is always low down, and its "sting" never rises at all. The chief stars, apart from Antares, are Lambda (1.6), Theta (1.9), Epsilon and Delta (2.3), Kappa (2.4), Beta (2.6), Upsilon (2.7), Sigma and Tau (2.8), Pi (2.9), Iota1 and Mu (3.0), G (3.2), and Eta (3.3), but Lambda, Upsilon, Kappa, Iota, Theta and Eta (3.3) are invisible in England, Regulus and Antares are on roughly opposite sides of Arcturus with Arcturus in the middle, which is of help in identifying Scorpio; Antares is also distinguished by its ruddiness and by the fact that, like Altair, it has a fairly bright star to either side of it - in this case Tau and Sigma Scorpii.
Double Stars. Antares has a companion of magnitude 5.1; distance 3"; P.A. 275°. The primary is of course red; the companion is green. It is a fine object.
Nu: magnitude 4.3,6.5; distance 41"; P.A. 335°. A wide, easy double. Each component is again double, but very close and difficult.
Beta: magnitudes 2.8,5.0; distance 1". There is a third star, magnitude 4.9, at 14".
Clusters. M.80. A splendid globular, lying roughly between Antares and Beta.
M.4. An open cluster. The stars in it are not brilliant, but the object is not hard to find, as it lies close to Antares.
SERPENS. The chief star in Caput is Alpha (2.6). R is an M-type variable; magnitude 5.7-14.4, period 357 days. M.5, a bright globular, lies near Alpha.
Map X. Pegasus, Andromeda, Pisces, Triangulum, Aries, Cetus, Aquarius, Sculptor, Pisces Australis
The chief group in this map is the Square of Pegasus, which in my view is much more difficult to identify than might be supposed, as most people expect it to be smaller and brighter than it really is. The best way to find it is by means of Cassiopeia, as Gamma and Alpha Cassiopeiae point directly to it. The line from Merak and Dubhe through Polaris will also reach the Square if extended far enough across the sky. Very rough risings and settings are as follows:
January 1st Rises in daylight, highest in daylight, sets at midnight.
April 1st Rises 2 a.m., highest in daylight, sets in daylight.
July 1st Rises in daylight, highest 5 a.m., sets in daylight.
October 1st Rises in daylight, highest 11 p.m., sets 7 a.m.
It is therefore at its best during the autumn. As is shown on Map VII, one of the stars of the Square is generally included in the neighbouring constellation of Andromeda (Alpha Andromeda=Delta Pegasi). Andromeda and Triangulum are described with Map VII.
PEGASUS. An important constellation, but not so conspicuous as is generally supposed. Alpha Andromedae (2.1) is the Square. The other chief stars of Pegasus are Epsilon (2.3, which is shown on Map VIII),Alpha (2.5), Beta (variable), Gamma (2.8), Eta (2.9), and Zeta (3.4). It is rather instructive to count the number of stars inside the Square visible with the naked eye; there are not very many of them.
Double Star. Xi: magnitude 4.0, 12; distance 12"; P.A. 108°. A difficult double, owing to the faintness of the companion. It is a binary, with a period of about a century and a half.
Variable. Beta: magnitude 2.3 to 2.8. An M-type semi-regular. Suitable comparison stars are Alpha (2.50) and Gamma (2.84). There is a very rough period of about 35 days.
ARIES. Celebrated as being the First Constellation of the Zodiac. It is not, however, very conspicuous. It lies between Aldebaran and the Square of Pegasus and has two fairly bright stars, Alpha (2.0) and Beta (2.7).
Double Star. Gamma: magnitudes 4.7, 4.8; distance 8".2; P.A. 000°. A fine easy double, very well seen with a small telescope. Rather unexpectedly,this is an optical double.
PISCES. The last constellation of the Zodiac, though owing to the precession of the equinoxes it now contains the First Point of Aries. It is large but faint, the brightest star being Eta (3.7). Pisces can be identified by the long line of rather faint stars running below the Square of Pegasus.
Double Stars. Alpha: magnitudes 4.3,5.3; distance 1".9; P.A. 292°.
Zeta: magnitudes 4.2,5.3; distance 24"; P.A. 060°.
CETUS. Part of this large constellation is shown in Map IV, and the chief star (Beta) in the key map I. Beta can be found by means of the Square of Pegasus, as Alpha Andromedae and Gamma Pegasi point towards it. Its proper name, Diphda, is often used, and it is an orange star suspected of variability. Not far from it is the M-type semi-regular variable T, which is reddish and has a magnitude range of from 5 to 7. Mira (Omicron), shown here, is described with Map IV.
SCULPTOR (a merciful abbreviation of the old name "Apparatus Sculptoris"). A very obscure constellation near Diphda. It contains no star as bright as the fourth magnitude and no objects of interest to the amateur.
AQUARIUS. Part of this Zodiacal constellation is shown in Map VIII, but most of it lies in the present map. The chief stars are Beta (2.9) and Alpha (3.0); (Map VIII); Delta (3.3) and Zeta (3.7). There is a striking group of orange stars centred around Chi (5.1); these are easy to identify and make pleasing telescopic objects under a low power.
Double Star. Zeta: magnitudes 4.4,4.6; distance 1".9; P.A. 256°. A fine binary,with a period of 360 years.
Variable. R: magnitude 6 to 11; period 387 days. An M-type long-period variable, not far from the star Omega2 (4.6).
PISCES AUSTRALIS. This small group is also termed Piscis Austrinus. It contains Fomalhaut, of the first magnitude, but no other star as bright as magnitude 4. Fomalhaut can be found by a line drawn from Beta through Alpha Pegasi, in the Square, and continued towards the horizon. From England, Fomalhaut is quite conspicuous near midnight in the autumn months. European observers, however, never see it to advantage. From southern countries it is very prominent and acts as a "guide" to the rather confused area of Southern Birds shown in the map on page 271.
Double Stars. Beta: magnitudes 4.4,7.8; distance 30"; P.A. 172°.
Gamma: magnitudes 4.5,8.5; distance 4".3; P.A. 262°.
Delta: magnitudes 4.3,10.6; distance 5"; P.A. 240°. Rather difficult, owing to the faintness of the companion.
The Southern Stars
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