Jyotisha is a one of the limbs (angas)of the Veda's called a Vedanga, Jyotish is considered the eyes so that humanity may have forsight, to be a seer of obstacles and be able to provide remedy. It was originally taught between a Guru and disciple, as in an the traditional oral traditiond, oral traditions preceed the book traditions of speculation and personal opinion. We do the best we can but when our roots from the oral are cut we lose our grounding. Jyotish is not just astrology, it is an accurate astronomy because it when they say the stars and planets are in a certain constellation, jyotish is accurate and can be checked as to what scientists at NASA are saying these placements are. Where as western astrology is out by 23 to 24 degree's.
A jyotishi should be a sadhaka in a deep yogic spiritual practice, always learning about evertyhing, and with Lord Ganesha's help everything is categorized.