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LX200 Learnings

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Posted by Daniel Johnson on March 18, 2003 04:45:40 UTC

First, try logging on to the Yahoo! LX200GPS support group, if you haven't discovered it. It is a highly active group for that line of scopes.
Second, avoid field derotators. They add length to the scope and generally prevent you from pointing straight up for that reason. Also, they require the perfect function in unison of three motors acting at constantly variable rates, rather than having one motor doing 99.9% of the work at a constant rate--and that one motor has very nice programmable permanent periodic error correction, thank you. Finally, your guide scope won't have a derotator on it. Oops.
Polar alignment doesn't require Polaris--in fact, I don't use Polaris. There are dozens of iterative methods that get you close quickly once you practice, and then the drift method fine-tunes you if you want. Iterate roughly as follows:
Point the polar axis mighty close to the pole by eye. Turn the tube so that it points up at the meridian and at about zero degrees declination--the scope seemes to expect to wake up in this position. Turn on the scope, and let it do the GPS thing. Then you will iterate between two stars chosen from the Named Star list. Star #1 should be close to the equator and close to the meridian. Star #2 should be much closer to the pole but NOT close to the meridian, i.e. as close as possible to having RA 6 hours ahead of or behing start #1. Go To star 1 (the scope will probably slew close to it, but if it misses by a kilometer just unlock the axes, move close by hand, then use the keypad). Center and Synch on Star 1 using the keypad. Then Go To star #2, but DO NOT Synch on it--use only the wedge controls to center star 2 after the scope is done slewing. Then Go To star 1, center and Synch on it again, then Go To star 2, DO NOT synch but again center with the wedge, and so on. Three to 5 iterations usually do it for me. I do the first couple using the telerad or finder, then switch to the eyepiece.
Daniel Johnson

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