ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

124 INDIAN LUNI-SOLAR ASTRONOMY
where D' means the Moon as corrected by the 1st and the 2nd
equations. Here the constant is wrong by −1' 18".
(4) His fourth equation or the annual equation
= ± 1/10 of the Sun's equation of apsis,¹
= ± 1/10 × (12 × 3438) / 360 sin (Sun's distance from the
apogee).
= ±11'27". 6 sin (Sun's distance from the apogee).
The modern value of the constant is 11' 10". Tycho found
it to be 4' 30". Horrocks' (1639) co-efficient was 11' 51".
As Candraśekhara was aware of Bhāskara's Bījopanaya, as
also of the work of Śrīpati, his merit here lies in the discovery
of the annual equation, and correction to the constant of
variation.
Thus we have seen that so far as the luni-solar astronomy
is concerned Indian astronomy is independent of Greek astronomy
in respect of astronomical constants, that Indian astronomy is
generally more accurate than Greek astronomy and that Indian
astronomers were not mere "calculators"². There were observers
who verified and corrected the old astronomical constants as
they came down from Āryabhaṭa and Brahmagupta, who also
found independently all the principal equations of the Moon.

1. Siddhānta darpaṇa VI. 13.
2. G.R. Kaye Hindu Astronomy, p. 60
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   Reference
   P.C. Sengupta : The Khaṇḍakhādyaka, 1934
   Karl Manitius's edition : Syntaxis.
   Godfray : Lunar Theory.