पञ्चसिद्धान्तिका (आचार्य वराहमिहिर - सूर्य, रोमक, पौलिश, वासिष्ठ एवं पितामह सिद्धान्त)

VIII.13 VIII. ROMAKA-SIDDHĀNTA — SOLAR ECLIPSE 189
Thus, the following has got to be done:
(i) The OEP for the time for which the parallax corrected latitude is required, is found, by
using the local ascensional differences.
(ii) Nonagesimal = OEP + 9 signs.
(iii) Find the declination of the nonagesimal, marking its direction north or south.
(iv) Sine (nonagesimal − Head of Rāhu) × 7/3 = latitude pertaining to nonagesimal. This is
north if (nonagesimal − Head of Rāhu) is within 6 signs, south otherwise.
(v) Corrected declination = declination ± latitude, found in (iv), (the upper sign of same direc-
tion, otherwise lower, the direction of the result being that of the greater.
(vi) ZDN = Latitude of the place ± corrected declinations, the upper sign if the corrected declina-
tion is south, lower sign otherwise. In the latter case, if the latitude is greater, the direction of ZDN
is south, if the declination is greater it is north).
The work is thus explained: In computing the solar eclipse it has been mentioned under VII.1,
that in the place of the Moon's latitude, the same corrected for parallax has got to be used. To get
the correction the sine of the ZDN is required. For ease of computation, the Romaka takes the
difference between the latitude of the place and the declination of the nonagesimal (the directions
being taken into consideration,) as the ZDN, the error being small as can be seen from the figure
under VII.1. This is given by verse 12 above.
Further, the parallax correction for latitude depending on sine ZDN is on the supposition that
the Moon moves on the ecliptic, which is only approximately true. Actually the Moon moves in its
orbit, and a small correction has got to be made for this, and the work of verse 11 above is intended
for this. Practically, all astronomers before the famous Bhāskarācārya II have given this rule, on the
surmise that taking a point on the Moon's orbit, corresponding to the nonagesimal, things will be
all right. But the mistake in this has eluded all these ancient astronomers, including the astute
Brahmagupta. It was Bhāskarācārya who detected their mistake, showed, by means of an example,
how the rule was wrong, and gave the correct rule. (Vide the Vāsanā-Bhāṣya at the end of Sūrya-
grahaṇādhikāra, Gaṇitādhyāya, Siddhānta Śiromaṇi).
From the rule given by verse 11, it can be inferred that according to this Siddhānta the obliquity
of the Moon's orbit, giving the maximum latitude of the Moon, is 280 minutes, (got from: 120 × 2
(1 + 1/6) = 120 × 7/3 = 280). We shall see that this agrees with the rule given by verse 14, giving
the Moon's latitude. But TS have adopted the incorrect reading, kharasāṃśasammitām and dividing
the doubled sine by sixty, got the latitude, which they are constrained to consider to be in degrees.
NP too, accept the same sense as TS with an emended reading kharasāptām apakramāṃśāt. By this
the maximum latitude according to the Romaka would be 4°. It is very strange that they do not see
this is too far from the correct value, highly improbable in the Romaka which they themselves praise
inordinately, and disagrees with their own (TS's) commentary under verse 14.
[नतिः बिम्बमानं च]
तज्ज्यार्द्धं शशिभुक्तिं हत्वा ‘धृतिभिः शतैः’ स्मृता [ऽवनतिः] ।
मध्यममानं त्रिंशद् भानोः शशिनश्चतुस्त्रिंशत् ॥ १३ ॥