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 [gamma] Virginis, a noted double. In 1756 the components were 6-1/2 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 4-1/2 seconds apart, situated as shown in Plate 3. They are nearly equal in magnitude (4), and both pale yellow.
The star [gamma] 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 3-1/5 seconds, the larger of the second, the smaller of the fourth magnitude; the former yellow-orange, the latter greenish-yellow.
Lastly, the star [iota] 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.
A HALF-HOUR WITH BOOTES, SCORPIO, OPHIUCHUS, ETC.
We now commence a series of observations suited to the third quarter of the year, and to the following hours:—Ten o’clock on the 22nd of July; nine on the 8th of August; eight on the 23rd of August; seven on the 8th of October; and intermediate hours on days intermediate to these.
We look first for the Great Bear towards the north-west, and thence find the Pole-star. Turning towards the north we see Capella and [beta] Aurigae low down and slightly towards the left of the exact north point. The Milky Way crosses the horizon towards the north-north-east and passes to the opposite point of the compass, attaining its highest point above the horizon towards east-south-east. This part of the Milky Way is well worth observing, being marked by singular variations of brilliancy. Near Arided (the principal star of Cygnus, and now lying due east—some twenty-five degrees from the zenith) there is seen a straight dark rift, and near this space is another larger cavity, which has been termed the northern Coal-sack. The space between [gamma], [delta], and [beta] Cygni is covered by a large oval mass, exceedingly rich and brilliant. The neighbouring branch, extending from [epsilon] Cygni, is far less conspicuous here, but near Sagitta becomes brighter than the other, which in this neighbourhood suddenly loses its brilliancy and fading gradually beyond this point becomes invisible near [beta] Ophiuchi. The continuous stream becomes patchy—in parts very brilliant—where it crosses Aquila and Clypeus. In this neighbourhood the other stream reappears, passing over a region very rich in stars. We see now the greatest extent of the Milky Way, towards this part of its length, ever visible in our latitudes—just as in spring we see its greatest extent towards Monoceros and Argo.