सिद्धान्तदर्पण (महामहोपाध्याय सामन्त चन्द्रशेखर सिंह - नग्न-नेत्र खगोल वेध एवं गणित महाकोश)

xlvi सिद्धान्त दर्पण
precession for all is about 20°, that for Asvini
(ά Arietes) and Uttara-bhadrapada (άAndromeda), the
two stars on either side of Revati, is about 24' each.
The question becomes more perplexing when
remember that Bhaskara, who certainly made a few
corrections, has given in most cases the same
longitudes as we have in the current Surya-
Siddhanta.
Our identfication of some of the stars may be
doubtful.¹ But taking all the star-longitudes into
consideration, we are forced to admit that somehow
or other there were errors of observation. Possibly,
these errors were partly due to the rude means of
observation, increasing the errors with the increase
of the zenith distance of the stars, and partly to
azimuth errors. One or all of the explanations must
be accepted as true, as we cannot suppose that any
one having the slightest pretension to practical
astronomy, however rough the instrument might
be, could make such gross errors in the simple
measurements required. To take the mean of the
star-longitudes for a solution of our problem is,
therefore, a wrong procedure, in as much as, we
are entirely in the dark as to the weight to be
attached to the determinations. We shall however,
make use of them in another way later on.
We now proceed to consider the third method,
which consists in analysing the dates in which there
was no ayanamsa. For this purpose, we require not
only the dates but also the rates of precession

1. Thus, if Asvini be identified with β Arietes and
   Uttarabhadrapada with y Pegasi, the amount of percession
   deducted from them becomes nearly equal and agrees
   with that obtained from Magha.