MARY W. WHITNEY. 247 
glass. After the latter date I lost sight of the star in 
the encroaching moonlight, and when the moon had 
passed, the star was too faint to be any longer followed 
in that glass. Perhaps it will not be out of place to give 
briefly the method for determining magnitude, which I 
used. It is very simple, suggested first by Argelander, 
and, as I use it, slightly modified by Prof. Pickering. 
First we must identify the star if it is not large enough 
to be recognized by the naked eye. For this purpose, 
by the aid of a good star catalogue, which gives both 
position and magnitude, we plot the stars whose right 
ascensions and declinations show them to be in the vi- 
cinity of the new body. Such, in the infinite variety of 
position and size presented by the heavenly bodies, that 
the picture formed by our grouping of neighboring stars 
is easily recognized as we sweep the telescope slowly 
over that portion of the skies which contains the sought 
for star. Andif in that group there is found one not 
included in our catalogue picture, the temporary is 
identified. This process of identification was uncalled 
for in the case of the Vova Andromeda, because of its 
singular position in the renowned nebula. But I needed 
to resort to it to identify the Vova Orionis. After the 
star is secured, certain other stars are selected, some 
brighter and some fainter than the star itself, and their 
magnitude determined from some trustworthy catalogue. 
Argelander’s Durchmusterwmg, a celebrated catalogue 
prepared at Bonn, is often used. It contains stars 
to the 9.5 magnitude. The new star is separately com- 
pared with a star slightly above it in magnitude, and 
with another slightly below it, and its relative position 
between the twoestimated. Thus if we determine it to 
lie half-way between the two we make our record a5 b, 
aand b representing our comparison stars. A similar 
comparison is made with other pairs of stars, the more 
the better, to secure accurate results. This very simple 
ple} 
