Thread: focus motor
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Old 15-10-2017, 02:01 PM
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sungrazer (Karen)
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Join Date: Jan 2007
Location: Sydney
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focus motor

Hi All

Has anyone else had this problem and how did you solve it.

I have a new electric motor focus running with FCUSB. Works just fine (ish)
Connects fine - moves fine so while I monitor the focus between filters it's no problem.

BUT

I want to use it with SGP without monitoring it - the way SGP works is that it counts the MS between each filter and uses that to adjust (it doesn't adjust based on fwhm for example). You calibrate it - it remembers, then it runs it on each filter - so it is important that the travel distance is correct). My problem is that the distance it travels to do 20000 ms in forward is different to the distance it travels in reverse.


When the camera (qsi683)is attached to the ED80 it doesn't return to the original point with the same MS used. It comes out 20000 and goes back in 20000 but needs another 3000 ms to reach the same starting point.

I suspect it doesn't like the weight of the camera, because it looks like it runs correctly when the camera is not attached.

One thing I did already try was to grind the focus sleeve on the telescope flat to be sure it was running straight. Unfortunately, that made no difference.

You can see the gap in the photo attached.

Any ideas. Is this likely to happen on all telescopes? What do others do to get SGP to work with en electric focusser?

Thanks
Karen
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