Varāhamihira

Varāhamihira was an early Indian astronomer.

He was one of the many Indian astronomers to describe the Celestial Sphere.

He wrote the Pañcasiddhāntikā, the Brḥatsaṃhitā, a version of Sūrya Siddhānta, and a version of Vāsiṣṭhasiddhānta.

Pañcasiddhāntikā
He wrote the Pañcasiddhāntikā circa 505 AD. His purpose, he writes, is to take the best of the preceding schools and make it clear.

The work also describes his view of the Earth, as an 'iron ball held in position in a cage of magnets'. He also discusses how residents of the North Pole (Devas, gods) would view the residents of the South Pole (asuras, demons) as 'upside down', and vice versa.

He also describes and five of the eighteen siddhāntas. The work also, as it regards the Vāsiṣṭhasiddhānta, gives calculations regarding lunar eclipses.

The work describes inaccuracies in the work of Bhadraviṣṇu, pointing out that his models do not match observation. He also describes some inaccuracies of Pādāditya, pointing out that the sunset does not occur at the same time on every place on the Earth

Varāhamihira also says that while the good astronomer will gain Dharma, the "bad astronomer who misleads people .... [will] go to hell".

Time
In, Varāhamihira gave a description of time, according to the Romaka Siddhānta and the Saura Siddhānta.


 * 1,80,000 solar years have 66,389 intercalary months, 10,45,095 elided days
 * luni-solar Romaka yuga = 2850 solar years
 * luni-solar Romaka yuga = 1050 intercalary months, 16,547 elided days
 * in a yuga:
 * solar years * 12 = solar months
 * solar months + intercalary months = synodic months
 * tithis = synodic months * 30 - elided days
 * civil days = tithis
 * sidereal days = civil days + solar years
 * moon's revolutions in a yuga = synodic months + solar years

Qualifications of an astronomer
Varāhamihira, in his work, describes the basic knowledge required of an astronomer:


 * The divisions of time: yuga, year, solstice, season, month, fortnight, day/night, yāma, muhūrta, nādī, prāṇa, truti, &c.
 * The reasons for four types of time measurement: Saura, Sāvana, Nākṣatra, and Cāndra (Solar, Terrestrial, Sidereal, Lunar)
 * Arguements comapring and contrasting these types, and their applications
 * The reasons for the intercalary months
 * The divisions of the ecliptic
 * Five of the Siddhāntas: Pauliśa, Romaka, Vāsiṣṭha, Saura, and Paitāmaha
 * Calculation of begin/end times of the 60-year-cycle, yuga, year, month, day, horā, & their lords.
 * Reconcile the differences of opinion of the Siddhānta's regarding ayana, using gnomon and water instruments
 * Causes of planet motion
 * Planet motion, in yojanas.
 * Forecast lunar and solar eclipses, and conjuctions of the moon with the Tārāgrahas
 * The Earth's movement and shape
 * Latitude
 * Lengths of day and night
 * Find the Carakhaṇḍas for a place
 * Finding time based on shadows and vice versa
 * Find the ghaṭis elapsed since sunrise