Page:Sewell Dikshit The Indian Calendar (1896) proc.djvu/19

7. The tithi, amâvâsyâ, pûrṇimâ. The moment of new moon, or that point of time when the longitudes of the sun and moon are equal, is called amâvâsyâ (lit. the "dwelling together" of the sun and moon). A tithi is the time occupied by the moon in increasing her distance from the sun by 12 degrees; in other words, at the exact point of time when the moon (whose apparent motion is much faster than that of the sun), moving eastwards from the sun after the amâvâsyâ, leaves the sun behind by 12 degrees, the first tithi, which is called pratipadâ or pratipad, ends; and so with the rest, the complete synodic revolution of the moon or one lunation occupying 30 tithis for the 360 degrees. Since, however, the motions of the sun and moon are always varying in speed^[1] the length of a tithi constantly alters. The variations in the length of a tithi are as follow, according to Hindu calculations:

The moment of full moon, or that point of time when the moon is furthest from the sun,—astronomically speaking when the difference between the longitudes of the sun and moon amounts to 180 degrees—is called pûrṇimâ. The tithi which ends with the moment of amâvâsyâ is itself called "amâvâsyâ", and similarly the tithi which ends with the moment of full moon is called "pûrṇimâ." (For further details see Arts. 29, 31, 32.)

8. The nakshatra. The 27th part of the ecliptic is called a nakshatra, and therefore each nakshatra occupies (⁠360°/27⁠ =) 13° 20′. The time which the moon (whose motion continually varies in speed) or any other heavenly body requires to travel over the 27th part of the ecliptic is also called a nakshatra. The length of the moon's nakshatra is:

It will be seen from this that the moon travels nearly one nakshatra daily. The daily nakshatra of the moon is given in every pañchâṅg (native almanack) and forms one of its five articles. The names of the 27 nakshatras will be found in Table VIII., column 7. (See Arts. 38, 42.)

9. The yoga. The period of time during which the joint motion in longitude, or the sum of the motions, of the sun and moon is increased by 13° 20′, is called a yoga, lit. "addition". Its length varies thus:

The names of the 27 yogas will be found in Table VIII., col. 12. (See Art. 39.)

10. The karaṇa. A karaṇa is half a tithi, or the time during which the difference of the longitudes of the sun and moon is increased by 6 degrees. The names of the karaṇas are given in Table VIII., cols. 4 and 5. (See Art. 40.)