"Mars causes accidents and burns and things like that, and when it makes an angle to Saturn, that means people need to be extra careful when handling hot things--"
-- Parvati Patil (OP27)
A type of Divination which relies on star charts and the time and date of a person’s birth.
The study of Astrology requires a careful study of star charts relating to the date of a person's birth. The students in Trelawney's Divination classes have to create complicated charts and determine which planets were where and how that all affects their lives. Based on astrological signs, Trelawney suggested that Harry must have been born in midwinter (GF13). When he taught the class, Firenze told the students that astrology was 'human nonsense' (OP27).
When Harry and Ron are given the task of creating their own star chart and using it to make a month's worth of predictions, they are forced to revert to the 'old Divination standby' and make it up (GF14).