Equal
Ancient Greek astrologers
12 equal houses · Ascendant as start · pole-resistant · simple math
How it divides the sky
Ascendant is the 1st house cusp; each next cusp adds 30°, the next +60°, etc. So if Asc is 18° Leo, the 2nd cusp is 18° Virgo, the 3rd is 18° Libra, etc. Difference from Whole Sign: the cusp locks to the Asc degree, not to the sign's start. Not quadrant-based; MC doesn't coincide with the 10th cusp.
When to use it
Many modern astrologers use Equal as an alternative to Placidus — because you may be troubled by Placidus's unequal house sizes. Margaret Hone was Equal's main advocate. If you say "house size difference distorts my reading," choose Equal.
History
Used since the Hellenistic period — most prominently in classical English literature. In the 20th century Margaret Hone popularized it in England with "The Modern Text-Book of Astrology."