Page:Sewell Dikshit The Indian Calendar (1896) proc.djvu/37

Five ghaṭikâs is not the exact limit, nor of course the fixed limit. The period varies from nil to about five ghaṭikâs, rarely more in the case of tithis, nakshatras, and karanas; but in the case of yogas it will sometimes reach seven ghatikas.

Calculations made by our method C will result in the finding of a "tithi index" (${\displaystyle t}$.), or a nakshatra or yoga-index (${\displaystyle n}$. or ${\displaystyle y}$.), all of which will be explained further on; but it may be stated in this connection that when at any ascertained mean sunrise it is found that the resulting index is within 30 of the ending index of the tithi, (Table VIII., col. 3), nakshatra or karaṇa (id. col. 8, 9, 10), or within 50 of the ending index of a yoga (id. col. 11), it is possible that the result may be one day wrong, as explained above. The results arrived at by our Tables, however, may be safely relied on for all ordinary purposes.

38. Nakshatras There are certain conspicuous stars or groups of stars in the moon's observed path in the heavens, and from a very remote age these have attracted attention. They are called in Sanskrit "Nakshatras". They were known to the Chaldœans and to the ancient Indian Âryas. Roughly speaking the moon makes one revolution among the stars in about 27 days, and this no doubt led to the number^[1] of nakshatras being limited to 27.

The distance between the chief stars, called yôga-târâs, of the different nakshatras is not uniform. Naturally it should be 13° 20′, but, in some cases it is less than 7°, while in others it is more than 20°. It is probable that in ancient times the moon's place was fixed merely by stating that she was near a particular named nakshatra (star) on a certain night, or on a certain occasion. Afterwards it was found necessary to make regular divisions of the moon's path in her orbit, for the sake of calculating and foretelling her position; and hence the natural division of the ecliptic, consisting of twenty-seven equal parts, came into use, and each of these parts was called after a separate nakshatra (see Art. 8). The starry nakshatras, however, being always in view and familiar for many centuries, could not be dispensed with, and therefore a second and unequal division was resorted to. Thus two systems of nakshatras came into use. One we call the ordinary or equal-space system, the other the unequal-space system. The names of the twenty-seven stellar nakshatras are given to both sets. In the equal-space system each nakshatra has 13° 20′ of space, and when the sun, the moon, or a planet is between 0°, i.e., no degrees, and 13° 20′ in longitude it is said to be in the first nakshatra Aśvinî, and so on. The unequal-space system is of two kinds. One is described by Garga and others, and is called here the "Garga system." According to it fifteen of the nakshatras are held to be of equal average (mean) length—i.e., 13° 20′,—but six measure one and-a-half times the average—i.e., 20°, and six others only half the average, viz., 6° 40′. The other system is described by Brahmagupta and others, and therefore we call it the "Brahma-Siddhânta" system. In its leading feature it is the same with Garga's system, but it differs a little from Garga's in introducing Abhijit in addition to the twenty-seven ordinary nakshatras. The moon's daily mean motion,—13 degrees, 10 minutes, 35 seconds,—is taken as the average space of a nakshatra. And as the total of the spaces thus allotted to the usual twenty-seven nakshatras, on a similar arrangement of unequal spaces, amounts to only 355 degrees, 45 minutes, 45 seconds, the remainder,—4 degrees, 14 minutes, 15 seconds,—is allotted to Abhijit, as an additional nakshatra placed between Uttara-Ashâḍhâ and Śravaṇa.

The longitude of the ending points of all the nakshatras according to these three systems