Yes, I meant his substantial astrological contributions.
Ptolemy, like all those making measurements of planetary positions, was working from a Geocentric perspective. Copernicus proposed the Heliocentric model, but with orbits that were PERFECT CIRCLES. With perfectly circular orbits, Ptolemy's Geocentric model was still the simpler of the two for making the actual calculations. Once Kepler discovered the Three Laws of Planetary Motion, the extreme simplicity ("elegance") of the Heliocentric model gave it supremacy over all Geocentric models.
Nevertheless, Astrology is a Geocentric coordinate system, wherein we can accept the Heliocentric model as an alternative perspective, and apply its accurate calculations from within the Geocentric Astrological framework. Modern Astronomers do this within their system of "Right ascension", which is a Geocentric format that makes locating celestial objects from the Earth, based on Coordinated Universal Time (UTC), extremely convenient. If you're planning on visually locating Planets and stars yourself, I would recommend using Right ascension.