Celestial Programming : Geographic Position of a Celestial Body (Approximate)

The Geographic Position of a celestial body is the point on the Earth's Surface where the body would be directly overhead (an Alt of 90°). This is primarily used in celestial navigation. This page is intended as a simple example for converting RA/Dec to a GP, positions are only adjusted for Precession, and not nutation, abberation, etc. Additionally the Sun position algorithm is only good to 1 degree.

$$ \begin{align*} \theta &= \delta \\ \phi &= \alpha - GST \end{align*} $$ $ \theta $: Latitude
$ \phi $: Longitude
GST: Greenwich Sidereal Time (Mean or Apparent depending on accuracy needs)
$ \alpha $: Right Ascension
$ \delta $: Declination