Astrology, for centuries regarded as identical with astronomy, has a legendary origin in India where its main purpose was ascertaining the correct dates and times for performing sacrifices. It is possible that some early astrological ideas came from Mesopotamia but this is less certain than the evidence of Greek influence. Indian authors clearly attribute much of their information to Hellenistic scientific sources.

As astrology established itself as a science the South Asian sub-continent regarded the Sun (Surya), the Moon (Soma), Mercury (Budha), Venus (Sukra), Mars (Mangala), Jupiter (Brihaspati), Saturn (Shani) as the seven conventional planets, while the moon was given two additional aspects, Rahu (its ascending node) and Ketu (its decending node).

Shani is often regarded as a bringer of bad luck, and is therefore frequently propitiated. He is described in some texts as holding a staff in one hand, having the other in the gift bestowing gesture (Varada mudra), and sitting on a lotus seat, while another text says he should hold a staff and a rosary and ride in a chariot.

Rahu is known as a demonic planet who periodically devours the moon, causing eclipses (or waning). He is often shown as a disembodied head because he stole the soma (ie the moon, where Soma is kept) and drank it. Vishnu saw this and beheaded him but, as the Soma had already passed through his head and throat, his head became immortal. — Hindu Gods and Goddesses