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

l · सिद्धान्त दर्पण
ayanamsa in Saka 1021 in the above manner, we
find that it was 9°31′ in that year. From this,
calculating backwards at 58″.68 a year, we come to
Saka 437 as the year of no ayanamsa. We also note
that the rate of precession reduced from the
ayanamsa in 1021, amounts to 57″.295 per year.
In his Karana-kutuhala, Bhaskara has roughly
given 11° as ayanamsa about Saka 1105. From this
at the rate of 60″ in a year, the rate assumed by
him, we are taken back to Saka 555, and, at the rate
of 57″.55 which we have found before, to Saka 423.
We also note that adopting his observation, the rate
amounts to 56″.624 per year.
To take another example, we mention Ganesa
who wrote his Grahalaghava in Saka 1442.
According to him the rate of precession is 60″ in a
year, and Saka 444 was without ayanamsa. These
premises lead us to infer that ayanamsa amounted
to 16°38′ in Saka 1442, which at the rate of 58″.1
carries us back to Saka 412, a-date which is the
earliest of all that we have hitherto obtained. But,
considering that the amount of ayanamsa reduced,
compared to the present amount, makes the rate at
low as 53″.4, we are lead to infer that his data were
wrong. It is to be observed, however, that the rate
of 58″.68 if adotped makes Saka 422 as the year
without ayanamsa.¹
We may almost guess the data from which
Ganesa derived his rate. It is likely he accepted 11°
as the amount of ayanamsa in 1105, as recorded by

1. An error in observing ayanamsa is not uncommon. One
   instance of it is furnished by Mahadeva who recorded
   13°45′ as the amount of ayanamsa in Saka 1238 (Dwivedi’s
   G.T.), thus making the rate since then 52″.5 in a year.