Historically, how did they first find the Heliocentric and Geocentric distances of the Planets? I would imagine that a rudimentary system of Right Ascension and Declination or at least a Azimuth and Altitude from a fixed base telescope was established. The system was based on the Astronomical Unit, au, of course. Did they use Solar Parallax? Kepler was the first person to get it right with the observations of Mars from Tycho Brahe. Who before that first observed the parallax distance from au?