Page:Popular Science Monthly Volume 46.djvu/314

300 of minute stars in and near it. The star γ is an irregular variable. In 1670 it is said to have almost disappeared, while at the beginning of the eighteenth century it was more than twice as bright as it is to-day. The reddish star S is also probably variable. In my Astronomy with an Opera Glass will be found a cut showing a singular array of small stars partly encircling δ. These will be widely scattered, even with the lowest power of a telescope.

Eastward from Canis Major we find some of the stars of Argo Navis. Σ 1097, of sixth magnitude, has two minute companions at 20″ distance, p. 311° and 312°. The large star is itself double, but the distance 0·8″, p. 166°, places it beyond our reach. According to Burnham, there is yet a fourth faint star at 31″, p. 40°. Some three degrees and a half below and to the left of the star just examined is a beautiful star cluster, No. 1551. Nos. 1564, 1571, and 1630 are other star clusters well worth examination. A planetary nebula is included in 1564. With very powerful telescopes this nebula has been seen ring-shaped. Σ 1146, otherwise known as 5 Navis, is a pretty double, colors pale yellow and blue, magnitudes fifth and seventh, distance 3·25″, p. 19°. Our three-inch will suffice for this.

North of Canis Major and Argo we find Monoceros and Canis Minor (map No. 3). The stars forming the western end of Monoceros are depicted on map No. 1. We shall begin with these. The most interesting and beautiful is 11, a fine triple star, magnitudes fifth, sixth, and seventh, distances 7·4″, p. 131°, and 2⋅7″, p. 103°. Sir William Herschel regarded this as one of the most beautiful sights in the heavens. It is a good object to try our three-inch on, although it should not be difficult for such an aperture. The star 4 is also a triple, magnitudes sixth, tenth, and eleventh, distances 3·4″, p. 178°, and 10″, p. 244°. We should glance at the star 5 to admire its fine orange color. In 8 we find a golden fifth-magnitude star, combined with a blue or lilac star of the seventh magnitude, distance 13″, p. 24°. Σ 938 is a difficult double, magnitudes six and a half and twelve, distance 10″, p. 210°. Σ 921 is double, magnitudes six and a half and eight, distance 16″, p. 4°. At the spot marked on the map 1424 we find an interesting cluster containing one star of the sixth magnitude.

The remaining stars of Monoceros will be found on map No. 3. The double and triple stars to be noted are S, or Σ 950 (which is also a variable and involved in a faint nebula), magnitudes sixth and ninth, distance 2·5″, p. 206°; Σ 1183, double, magnitudes five and a half and eight, distance 31″, p. 326°; Σ 1190, triple, magnitudes five and a half, tenth, and ninth, distances 31″, p. 105, and 67″, p. 244. The clusters are 1465, which has a minute triple star near the center; 1483, one member of whose swarm is red; 1611, very small but rich; and 1637, interesting for the great number