Page:Popular Science Monthly Volume 30.djvu/779

Rh and, at nine o'clock in the evening, is below the large star. It is of the seventh magnitude. With a large field-glass several smaller companions may be seen, and a very excellent glass may show an 8·5 magnitude star almost hidden in the rays of the seventh magnitude companion.

With the aid of the accompanying map of Ursa Minor, which is the constellation to which the pole-star belongs, find the star Beta (ß), which is also called Kochab (the star marked α in the map is the pole-star). Kochab has a pair of faint stars nearly north of it, about one degree distant. With a small glass these may appear as a single star, but a stronger glass will show them separately.

And now for Ursa Major and the Great Dipper—Draco, Cepheus, Cassiopeia, and the other constellations represented on the map, being rather too near the horizon for effective observation at this time of the year. First, as the easiest object, look at the star in the middle of the handle of the Dipper (this handle forms the tail of Ursa Major), and a little attention will show you, without the aid of a glass, if your eye-sight is good, that the star is double. A smaller star seems to be almost in contact with it. The larger of these two stars is called Mizar and the smaller Alcor—the Horse and his Rider the Arabs said. Your glass will, of course, greatly increase the distance between Alcor and Mizar, and will also bring out a clear difference of color distinguishing them. Now, if you have a very powerful glass, you may be able to see the Sidus Ludovicianum, a minute star which a German astronomer discovered more than a hundred and fifty years ago, and strangely enough, taking it for a planet, named it after a German prince. The position of the Sidus Ludovicianum with reference to Mizar and Alcor, is represented in the accompanying sketch. You must look very sharply if you expect to see it, and your opera-glass will have to be a large and strong one. A field glass, however, can not fail to show it.

Sweep along the whole length of the Dipper's handle, and you will discover many fine fields of stars. Then look at the star Alpha (α) in the outer edge of the bowl nearest to the pole-star. There is a faint star, of about the eighth magnitude, near it, in the direction of Beta (β). This will prove a very difficult test. You will have to try it with averted vision. If you have a field-glass, catch it first with