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

340 PAÑCASIDDHĀNTIKĀ XVIII.37
The text then gives a table from which for a given mean longitude the true position on the true date can
be obtained. Since the Sun's position has to be 12 degrees behind the true position of Mercury, the
same correction applied to Mercury has to be applied to the Sun. That means, keeping in mind that
the Sun moves one degree in one day approximately, the true date is ahead of the mean date by as
many days as the number of degrees in the correction, if the correction is positive, and vice versa.
Consequently, the number of days elapsed since the (true) rising is also modified by the same
number of days, reduced, if the correction is positive, and vice versa.
Having got the true Mercury as on the true date of rising and the number of days elapsed since
rising, we have now to get the degrees moved by Mercury during these remaining days in the
synodic cycle. For this purpose the synodic period is divided into several sections just as in the case
of other planets. In the case of Mercury the division is made into four sections or gati-s. The first is
from rising to starting of retrogression, the second is the period of retrogression, the third is from
end of retrogression or anuvakra to setting, while the fourth is from setting in the east to rising in
the west. The number of days for each section and the movement are not constant but vary
depending upon the position of Mercury in the zodiac. Accordingly, tables giving these values for
each of the twelve signs are given in the text. With the help of these tables we can trace the move-
ment of Mercury during the remaining days and finally arrive at its position.
What is new in the case of Mercury is the method of interpolation within these tables. For other
planets no specific method of interpolation is suggested, with the result we assume linear interpo-
lation. But here a second degree interpolation is suggested for certain sections.
TS and NP do not appear to have understood the procedure nor the rationale expounded by
these verses, as could be gauged from the emendations they make and explanations they give to the
verses.
[बुधमध्यम्] [बुधचारः]
(दद्यात् सप्तचतुष्कान्) द्युगणे त्र्यंशं च 'वसु'गुणो भागः |
'मुनियमनवके'रपि (रौहिणस्य) वेद्या, दिनाष्टांशाः || ३६ ||
[हत्वा] चतुर्भिरुदयान् नाड्यः शोध्या बुधस्य दिवसेभ्यः |
'त्रिरसयम'घ्नानुदयान् 'रामार्णव' वर्जितान् छिन्द्यात् || ३७ ||
'नवयमवसु [भि] र्मध्यमथो सक्रमानुदयांशैः क्रमाद् |
Mean Mercury
36-38a Add to the ahargaṇa seven times four, i.e., 28, and a third. Multiply by
eight and divide by 927. The quotient is the risings of Mercury. Take the
eighth part of the remainder and deduct therefrom, in nāḍikās, one fourth of
the risings, and the result is the (remaining) days of Mercury. Multiply the ris-
36a. A. दद्या B. सप्तनुक्कान् D. दिनाष्टांशः
b. B. द्यगणो A. त्र्यंशः; B. त्र्यंश 37a. A.B. कृत्वा
B. गुणभागः D. भाव्यः b. A. दुधस्य; B. बुछस्या
c. A. नवकै c. A.B. त्रिदशयमध्नान्; D. [अद्रिदशयम्] यमध्नान्
d. A.B. रोचितस्यः C. रोहिणस्य; D. रोचिताः स्युः B. ॰नुदयां
A. मेद्या; B. मेधा; D. शोध्यो d. B. रामणववर्जितान्; D. पाण्डववर्जिते श्छिन्द्यात्