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

Introduction xlv
as its longitude.¹ This is however, less than the
amount obtained above. It is clear therefore that
either the star Revati is not ζ Piscium, or it did not
mark the initial point. No doubt exists about the
identity of the star, neither can we suppose all the
Siddhantas false in their assertion.
The latitudes and longitudes of thirty-four
others stars are given in the Surya-Siddhanta. They
were not measured in the usual way. But from the
express instructions as to the method of
measurement adopted, we understand that the
so-called longitudes, Dhurvas, are the longitude of
the Right Ascensions of the stars supposing them
to be on the ecliptic, and that the latitudes
(Vikshepas) are the distances, north or south, of the
stars from the ecliptic, measured along the
declination circles passing through the stars. Now,
taking only the 27 stars of the zodiac, and
comparing their reduced Dhruvas with their present
longitude, we find ourselves confronted with a
curious result.² The difference between the recorded
and the present longitudes is not the same for every
star. Indeed, it varies from about 18° to 24°.
Omitting Visakha, of which I am not certain,
the mean difference of the longitudes of the stars
of the first half of the zodiac, i.e. from Asvini to
Chitra is 21°, while that of the stars of the second
half amounts to 19° only. So, while the mean
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1. The modern Surya-Siddhanta gives 359°50′ as the
   longitude of the star Revati. This would make the present
   ayanamsa greater by 10′ only.
2. I understand that Prof. Whitney has discussed the point,
   and regret that I have no access to his edition of the
   Surya-Siddhanta at present.