The distance separating the components is about 3 seconds, perhaps more; it appears to have been slowly increasing during the past ten or twelve years.

Smyth assigns to this system a period of revolution of 980 years, but there can be little doubt that the true period is largely in excess of this estimate.
Observers in southern latitudes consider that the colours of the components are yellow and blue, not orange and green as most of our northern observers have estimated them.
A little beyond the lower left-hand corner of the map is the star [delta] Serpentis, in the position shown in the Frontispiece, Map 3.
This is the star which at the hour and season depicted in Map 2 formed the uppermost of a vertical row of stars, which has now assumed an almost horizontal position.

The components of [delta] Serpentis are about 3-1/2 seconds apart, their magnitudes 3 and 5, both white.
The stars [theta]^{1} and [theta]^{2} Serpentis form a wide double, the distance between the components being 21-1/2 seconds.

They are nearly equal in magnitude, the primary being 4-1/2, the secondary 5.

Both are yellow, the primary being of a paler yellow colour than the smaller star.