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GSO Focuser

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#1 BobH



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Posted 20 January 2013 - 07:16 AM

I have a GSO 2-speed focuser which came with a used telescope. It currently has a 2-inch diagonal attached and a 16mm Nagler. Yesterday afternoon I was trying to observe the moon, so was at an altitude of about 60 degrees. Focuser would not hold focus and eventually just slipped out to the fully extended position. Adjusting the tension and locking screws had no effect.

AmI expecting too much? Is that too much weight for a GSO at that altitude?

I'm familiar with the procedure for adjusting one of these focusers to be smoother, but if it should be able to handle that weight at that altitude, how can it be adjusted?


#2 Jon Isaacs

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Posted 20 January 2013 - 08:02 AM

AmI expecting too much? Is that too much weight for a GSO at that altitude?

You don't say what sort of telescope this is on, is it a refractor or SCT that also has the added weight of a diagonal?

That said, a 16mm Nagler Type 2 weighs just about 1 lb. I have a couple of GSO focusers on Newtonians and they handle considerably more weight without a problem, the 20mm Type 2 + Paracorr is over 3 lbs.

Just to be sure, you have the focuser lock backed out all the way and the tension is towards the maximum?

About all I can suspect is that the drawtube and pinion shaft need cleaning or that one of the 4 bearings that the drawtube rides on has come loose.


#3 MikeCMP


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Posted 20 January 2013 - 01:04 PM

I had some trouble with one I had gotten used. The previous owner must have disassembled it to lube, but forgot to put the bushing in the right spot. Make sure there is a U channel plastic bushing pushing up against the focuser shaft, otherwise it will not work.


#4 Don Taylor

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Posted 20 January 2013 - 06:05 PM

One of mine (purchased new) - the u-shaped plastic piece split in use so I made a replacement from a nylon bushing. Symptoms are the same as you describe. See if the u-shaped bushing is cracked or split. Don't know who might stock spares but I would start with agena astro.

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