exact location of the objects of interest, in terms of Right Ascension and Declination.
For the most part only double stars with a primary of the sixth magnitude or brighter are given, as it is difficult te direct the telescope at a star of lesser magnitude unless its position is accurately known.
In searching for double stars many faint yet beautiful pairs and triples are observed, so that it is well to have such a book as Webb's, in order that these objects can be identified.
The diagrams include over three hundred double stars, and the sight of these and the many fine clusters and nebula mentioned should afford the happy possessor of a telescope many hours of keen enjoyment.
Considerable discrepancy will be noted in the colors assigned to the double stars, and those observed. The coloring in many cases is at best elusive, and atmospheric conditions and peculiarities of vision play an important part in determining it. In a number of cases the colors are very pronounced and render the object of surpassing beauty, as for instance in the great favorite (β) Cygni. The first color given is that of the primary or brightest star, the second color given is that of the companion,
The position angle measures the inclination to the meridian of a line drawn through the double stars. It shows the observer where to look for the companion star, and is reckoned from 0 degrees to 360 degrees, beginning
