Sent: Monday, August 15, 2011 17:00:05 From: Yannick Dutertre (email@example.com) I was playing around with an ETX 125 when I noticed that when turning it 360 degrees, there was an angle of about 30 degrees where it became noticeably more difficult to turn, as if there was some chaffing somewhere on the base. This caused the slewing at slow rates in these areas to become VERY jerky: at speeds 1 through 4, the telescope would move in noticeable increments (causing a phenomenon of it tracking jerkily ; as one of the user feedback from November 16, 2004 says: "when it is tracking it will hold a star fairly well, (there is a bit of drift) but then every 15 to 30 seconds the tracking will jerk the star back to center. The RA motor seems to make a bit of a straining sound before the jerk back" The slewing outside of this 30 degrees danger zone was perfect (besides the backlash in the nylon gears but one can't beat physics although training/RA percent does help). After useless inspections of the drive (it looked absolutely perfect and I couldn't find an issue there), I noticed that in the 30 degrees danger zone, the RA setting circle would become very difficult to turn. And then I noticed that it was somehow getting stuck: it was too wide, and was actually chaffing on the mount, causing the jerky movement. Removing the setting circle and carefully making it less wide by 1mm or so using scissors solved the issue. It is very surprising that the whole ETX experience could be spoiled by such a problem! Now one interesting thing is that I also checked on the demo ETX 125 at a shop (new model from 2011), and it had the exact same problem! Could this problem (that is not so easy to spot as it affects a 30 degrees angle and is not *that* bothersome because the scope does catch up eventually) be under reported? As such I think this could be worth checking for beginners in case of problems, before opening the base. Best regards, Yannick
And I found that out thanks to your advice of turning the scope from stop to stop to evenly spread the lubrication. So I guess one more beginner advice is to try to feel chafing when doing that...
Go back to the Tech Tips page.
Go back to the ETX Home Page.