They mostly get it from books about Astrology, written by other people who learned it from other books about astrology, all the way back to some prehistoric dude who basically pulled it out of his astrology.
Super Astrologer
Walter Koch - astrologer - died in 1970.
Walter Koch - astrologer - was born in 1895.
Julia Parker - astrologer - was born in 1932.
John Harvey - astrologer - died in 1592.
John Harvey - astrologer - was born in 1564.
John Partridge - astrologer - was born in 1644.
Jim Lewis - astrologer - was born in 1941.
Jim Lewis - astrologer - died in 1995.
poosamuthu was the very famous astrologer at vaitheeswaran koil
The Astrologer - 1908 was released on: USA: April 1908
The Astrologer - 1975 I was released on: USA: December 1975