The star κ Herculis is not shown in the map, but may be very readily found, lying between the two gammas, γ Herculis and γ Serpentis (see Frontispiece, Map 2), rather nearer the latter. It is a wide double, the components of fifth and seventh magnitude, the larger yellowish-white, the smaller ruddy yellow.[5]
Ras Algethi, or α Herculis, is also beyond the limits of the map, but may be easily found by means of Map 2, Frontispiece. It is, properly speaking, a multiple star. Considered as a double, the arrangement of the components is that shown in Plate [3]. The larger is of magnitude 3½, the smaller of magnitude 5½; the former orange, the latter emerald. The companion stars are small, and require a good telescope to be well seen. Ras Algethi is a variable, changing from magnitude 3 to magnitude 3½ in a period of 66⅓ days.
The star ρ Herculis is a closer double. The components are 3"·7 apart, and situated as shown in Plate [3]. The larger is of magnitude 4, the smaller 5½; the former bluish-white, the latter pale emerald.
There are other objects within the range of our map which are well worthy of study. Such are μ Draconis, a beautiful miniature of Castor; γ1 and γ2 Draconis, a wide double, the distance between the components being nearly 62" (both grey); and γ1 and γ2 Coronæ, a naked-eye double, the components being 6' apart, and each double with a good 3-inch telescope.
We turn, however, to another region of the sky. Low down, towards the south is seen the small constellation Corvus, recognised by its irregular quadrilateral of stars. Of the two upper stars, the left-hand one is Algorab, a wide double, the components placed as in Plate [3], 23"·5 apart, the larger of magnitude 3, the smaller 8½, the colours pale yellow and purple.
There is a red star in this neighbourhood which is well worth looking for. To the right of Corvus is the constellation Crater, easily recognised as forming a tolerably well-marked small group. The star Alkes, or α Crateris, must first be found. It is far from being the brightest star in the constellation, and may be assumed to have diminished considerably in brilliancy since it was entitled α by Bayer. It will easily be found, however, by means of the observer's star maps. If now the telescope be directed to Alkes, there will be found, following him at a distance of 42·5 s, and about one minute southerly, a small red star, R. Crateris. Like most red stars, this one is a variable. A somewhat smaller blue star may be seen in the same field.
There is another red star which may be found pretty easily at this season. First find the stars η and ο Leonis, the former forming with Regulus (now lying towards the south-west, and almost exactly midway between the zenith and the horizon) the handle of the Sickle in Leo, the other farther off from Regulus towards the right, but lower down. Now sweep from ο towards η with a low power.[6] There will be found a sixth-magnitude star about one-fourth of the way from ο to η. South, following this, will be found a group of four stars, of which one is crimson. This is the star R Leonis. Like R Crateris and R Leporis it is variable.
Next, let the observer turn towards the south again. Above Corvus, in the position shown in the Frontispiece, there are to be seen five stars, forming a sort of wide V with somewhat bowed legs. At the angle is the star γ Virginis, a noted double. In 1756 the components were 6½ seconds apart. They gradually approached till, in 1836, they could not be separated by the largest telescopes. Since then they have been separating, and they are now 4½ seconds apart, situated as shown in Plate [3]. They are nearly equal in magnitude (4), and both pale yellow.
The star γ Leonis is a closer and more beautiful double. It will be found above Regulus, and is the brightest star on the blade of the Sickle. The components are separated by about 3⅕ seconds, the larger of the second, the smaller of the fourth magnitude; the former yellow-orange, the latter greenish-yellow.
Lastly, the star ι Leonis may be tried. It will be a pretty severe test for our observer's telescope, the components being only 2"·4 apart, and the smaller scarcely exceeding the eighth magnitude. The brighter (fourth magnitude) is pale yellow, the other light blue.