Old 17-12-2014, 07:11 AM
pjphilli (Peter)
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Rc-8 focuser problem

I am having problems with my GSO RC-8 Ritchey Chretien focuser.
I am currently operating it with a light weight camera but although I tighten up the underneath tension adjustment screw to the extent that the adjustment knob is difficult to turn the focuser still slips in and out
owing the the weight of the camera. In fact the adjustment screw tension seems to have little effect on the focuser movement.
Cheers Peter
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Old 17-12-2014, 08:30 AM
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lazjen (Chris)
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If that's anything like the one on the RC10, I found it unreliable and replaced it with a Moonlite instead. I've had no problems with focus slipping since the change.
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Old 17-12-2014, 09:00 AM
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Cherap fix - take the pinion out of the focuser. Slip on a suitable size of shrink tube, shrink it, and reinstall pionion (adjusting the tensioners appropriately to permit the larger diameter).

I did this on several Skywatcher Crayfords, and it works well.

Get one of Stellarvue's new replacement rack and pinion dual speed units. SMOOTH, and hold weight very well.
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Old 18-12-2014, 10:46 AM
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The focusors supplied with the RC's by GSO are junk. You will be better off replacing it with a quality focusor.
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Old 18-12-2014, 02:03 PM
pjphilli (Peter)
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Thanks all for your assistance. I pulled the RC scope's focuser apart and found the problem.
The adjustment screw that puts pressure of a pad to move the rotating adjustment shaft against the inner focuser rail is on a very flimsy plastic assembly. This had cracked thus not allowing the screw to exert the required pressure.
See attached photo for my fix. The small 12 gauge plate provides a firm base. The focuser now works nice and smoothly.
How this plastic fitting outlasted the scope's guarantee period I don't know. It is moulded in a most flimsy fashion. I am happy with the performance of my GSO RC scope otherwise. Paul, you are right about the focuser. Plastic is good but how often do we see something ruined
by its failure?
Cheers Peter
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