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ETX-125 image jumps up and to the right

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#1 smartin53

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Posted 18 November 2012 - 03:43 AM

I know this gets asked a lot but I of course am having some tracking issues when adjusting the view.

Whenever I move the object to try and center it, it adjusts with no issues, but then after a second or so the object will suddenly move up and to the right in the view before coming to a stop again. To get the object centered, I have to usually place it at the lower left edge of the view and hope it stops near center.

Now, I know I can send it to Meade or get it Supercharged, but I wanted to see if anyone had any thoughts. I'm actually good with doing repairs to mechanics but I'd want to get a good idea where to look if I were to try something myself.

#2 nytecam

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Posted 19 November 2012 - 04:53 AM

Yes - even after 'training' the ETX seem to have a mind of its own and wanders-off - very irritating. I have three ETX-70s [job lot!] and they all do it after goto, centering and syncing. Sometimes they settle down - somewhat ;-(

#3 rmollise

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Posted 20 November 2012 - 08:10 AM

Meade won't supercharge it--or do any other sort of service to the scope these days, I'm afraid. Doc Clay Sherrod will, if the scope really needs it. Any time you get tracking problems with an ETX, the solution is almost always TRAIN DRIVES, being sure to do it carefully and do both the altitude and azimuth axes. ;)

#4 jgraham

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Posted 20 November 2012 - 08:55 AM

This is a well-known behavior called rubber-banding. There's a section on Mike Weasner's Might ETX Site that talks about how to reduce it. The first thing to try is a master reset of the controller, recalibrate the motors, and retraining the drives. Be sure not to skip the calibrate motors step. Doing your fine slewing using a slow slew rate also seems to help. It's been so long since I've done this I'd suggest checking with Mike's site to get the details.

#5 REC

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Posted 20 November 2012 - 11:23 AM

Mine does that too, but not from the drive, but focuser. Every time I try to adjust the fine focus the image moves across the FOV....very irritating.

Bob






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