[Mark_Heli (Mark)]

With a little extra time over XMAS / NY, I have been working on creating a 'Telescope Simulator' to show how the sky changes as a telescope moves.

I have made good progress, but hit a question around Sidereal Time and Right Ascension.

I understand that Sidereal time is the time taken for the earth to complete 1 rotation around it's axis which takes 23 hours, 56 mins and 4 seconds (of Solar time). Stars will return to the same position at the same sidereal time each day. Sidereal time can be determined by a Star's RA as it crosses the meridian.

Right ascension measures the angle around the celestial equator and is measured in degrees or hours with 24 hours (360 degrees) being a full rotation.

However I am trying to reconcile how Sidereal time (23h, 56m, 4s per day) aligns with RA (24 hours per day) - the 2 must align for stars to be in the same position each sidereal day.

Is it that Sidereal time takes 23h, 56m, 4s of Solar time, however Sidereal time still takes 24 hours using sidereal hours, minutes & seconds - i.e:

Sidereal day = 23h, 56m, 4s (solar time) = 24h sidereal time.

Hopefully the question makes sense.

Thanks,
Mark