How does one draw a star chart like this?
I have:
- a star database with coordinates (right ascension - RA, declination - DEC),
- observer coordinates (latitude, longitude) and
- time of observation.
I need a formula which considers these parameters (mapping star coordinates to a 2D image). e.g.
starX = (90-abs(DEC)) * cos(RA)
starY = (90-abs(DEC)) * sin(RA)