Quote:
Originally Posted by JohnG
Oops, actually meant to say 1 to 2 arc minutes  |
Thats ok JohnG, I knew what you meant.
1 to 2 arc seconds is still achievable.
But, you will be limited by your seeing conditions and patients. The latter in particular. I spent five hours getting down to 15 arcsecs azimuth and 17 arcsecs altitude polar alignment error. I had fun doing it though as I was testing the new PEMPro 2.0 beta drift alignment proceedure which makes drift aligning a breeze certainly with a goto scope. Automatically slews to the area of the sky for either azimuth or altitude adjustment, finds a star and starts telling you how much you have to adjust. Too easy.
The thing that really frustrated me is that you don't know how many turns (or fractions of a turn) on the azimuth or altitude adjustment controls corresponds to arcsecond movements. Towards the end I was making adjustments so tiny to get things settled. I have subsequently come across someone that has actually measured the adjustments on the Titan so I now know - Altitude = 60 arcminutes is approx one full turn; Azimuth = 37 arcminutes per millimeter (very fine). Also when you lock down the adjustment controls you experience shifts (due to the mount design) so you need to tweak some more. Sent me crazy - now you can understand why accurate polar alignment under 1 arcminute took five hours!
Something to note for Gemini users who are using the integrated polar alignment features of this telescope control system. The A: and E: values after each additional alignment are not displayed as arcseconds or degrees, but in arcminutes. Hence if you are using this system, the best you'll get is 1 arcminute from the pole - under normal circumstances this is probably good enough anyway. The only reason why I went that extra mile was because its a permanent set up and worth the effort. I wont have to redo the alignment, though I do check it quarterly.
Here is another good reference site with great formulas to calculate drift/rotation -
http://www.stargazing.net/yizen/fieldrotation.html