RA/DEC vs GoTo
Posted 26 December 2012 - 04:19 AM
long story short I was doing some AP with my C8 and CGEM and I noticed that my GoTos were spot on while my RA/DEC were low (they were just UP and out of the EP) so I kept having to bring them down into the EP. Anyone have a reason this would happen so I dont keep doing it lol...
Objects were about 40 deg-ish in the west and I was getting ra/dec from stellarium.
Posted 26 December 2012 - 05:19 AM
make sure that, when you did the initial GoTo alignment, only use the up and right buttons for the final align on each star. This will ensure that all of the slack is taken up.
Posted 26 December 2012 - 12:23 PM
Some scopes use J2000, some the current epoch. I don't know what Stellarium reports but you need to use the same as the mount.
Hope this helps,
Posted 27 December 2012 - 08:30 PM
Chris, I think Stellarium displays both if I remember correctly. Can you elaborate a little more as to the difference? Thats something I know NOTHING about lol....
Posted 28 December 2012 - 04:54 AM
Star positions in charts are usually converted to a particular date or epoch and the current one is usually the start of the year 2000, J2000.0.
The difference in position from 2000 to now will be of the order of 13 arc minutes and this is enough to move the position of an object by a noticeable amount.
Hope this helps, it's a very simple explanation and there are much fuller ones on the web.
Posted 28 December 2012 - 11:06 AM
Use 3 calibration stars during alignment to correct cone error. Check your polar alignment too. For visual, centering Polaris in the polar scope is adequate. For imaging, you may want to drift align.