Hi
was looking for threads explaining Dec and RA gradations for EQ mount setting circles and found this thread.
I'm kind of getting my head around the Equatorial co-ordinate system and can understand how RA is divided into 24hrs, but can someone explain the How the Dec co-ordinates work.
I'm using an equatorial fork mount, and the RA axis is set to 38deg for Melbourne. That said, if I align my RA axis to point to the SCP, and the tube is parallel to the RA axis, my understanding is that the Dec is 90Deg. But I read that the Dec is divided into 4 quadrants of 90 deg.
So if I move my OTA on the Dec axis by 90 deg toward azimuth (alt/az) or overhead, would that be 0 deg Dec? what happens if I move further up?
to clarify, I'm starting Dec at 90 deg pointing to the SCP when RA is aligned to SCP, I then move only along Dec by 90 towards North, then Dec becomes 0, and how does the Dec axis increment or decrement? to -10deg, -20 deg and so on?
found this pic
http://en.wikipedia.org/wiki/File:Se...rial_mount.jpg
secondly, in the eq co-ordinate system, if all objects have constand RA and Dec co-ordinates, what actually changes depending on time of day? is it the hour angle? I'm using stellarium to visualize.