Page:Popular Science Monthly Volume 46.djvu/309

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PLEASURES OF THE TELESCOPE.

At the lower end of the Sword is the star ι, somewhat under the third magnitude. Our three-inch will show that it has a bluish companion of seventh or eighth magnitude, at a little more than 11" distance, p. 142°, and the larger apertures will reveal a third star, of tenth magnitude, and reddish in color, distant 49", p. 103°. Close by ι we find the little double star Σ 747, whose components are of five and a half and six and a half magnitudes respectively, and separated 36", p. 323°. Above the uppermost star in the Sword is a small star cluster, No. 1184, which derives a special interest from the fact that it incloses a delicate double star, Σ 750, whose larger component is of the sixth magnitude, while the smaller is of the ninth, and the distance is only 4⋅3", p. 59°. We may try the four-inch on this object.

Having looked at α (Betelgeuse), the great topaz star on Orion's right shoulder, and admired the splendor of its color, we may turn the four-inch upon the star Σ 795, frequently referred to by its number as "52 Orionis." It consists of one star of the sixth and another of sixth and a half magnitude, only 1⋅5" apart, p. 200°. Having separated them with a power of two hundred and fifty diameters on the four-inch, we may try them with a high power on the three-inch. We shall only succeed this time if our glass is of first-rate quality and the air is perfectly steady.

The star λ in Orion's head presents an easy conquest for the three-inch, as it consists of a light-yellow star of magnitude three and a half and a reddish companion of the sixth magnitude; distance 4", p. 43°. There is also a twelfth-magnitude star at 27", p. 183°, and a tenth or eleventh magnitude one at 149", p. 278°. These are tests for the five-inch, and we must not be disappointed if we do not succeed in seeing the smaller one even with that aperture.

Other objects in Orion, to be found with the aid of our map, are: Σ 627, a double star, magnitude six and a half and seven, distance 21", p. 260°. O Σ 98, otherwise named ι Orionis, double, magnitude six and seven, distance 1", p. 218°, requires five-inch glass; Σ 652, double magnitudes six and a half and eight, distance 1·7", p. 184°; ρ, double, magnitudes five and eight and a half, the latter blue, distance 7", p. 62°, may be tried with a three-inch; τ, triple star, magnitudes four, ten and a half, and eleven, distances 36", p. 249°, and 36", p. 60°. Burnham discovered that the ten-and-a-half magnitude star is again double, distance 4", p. 50°. There is not much satisfaction in attempting τ Orionis with telescopes of ordinary apertures; Σ 629, otherwise m Orionis, double, magnitudes five and a half (greenish) and seven, distance 31·7", p. 28°, a pretty object; Σ 728, otherwise Α 32, double, magnitudes five and seven, distance 0·5" or less, p. 206°, a rapid binary, which is at