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RAO 76/1200 focuser replacement?

classic equipment refractor
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#1 Barnsey123

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Posted 24 September 2020 - 03:45 AM

Hi all,

 

I have a bent axle on my RAO 76/1200 (see pic below).  I've tried straightening it in a vice and it's a bit better but it's not right. As you turn the wheels it alternates between smooth and stiff.  When it's stiff it's shifting the diagonal slightly and moving the image to one side and it becomes very blurry. Am I making sense?  It's difficult to get focus although I managed OK on Mars the other night.

 

The original owner can't remember what happened to the scope originally but it's received a hell of a whack at some point.

 

So...options....should I persist in trying to straighten the axle and hope I don't break it or maybe replace the entire focuser?   I know replacement may be sacrilege  as it contains the maker details and SN but what do I do? Has anyone got a spare axle?  The original focuser was amended back in the day to make it accept 1.25" ep's (from .965) and it does feel a bit loose so it's not exactly a pristine original.

 

I've looked online for a solution but options seem limited (or non-existent AFAICT)

 

Would welcome anyones thoughts.

 

Focus Wheel

 



#2 Senex Bibax

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Posted 24 September 2020 - 07:31 AM

A**ebiscuits! I have the same problem with a COC 60mm I bought recently. I'm going to try a trick with three pieces of hard wood in my vise, two at the ends of the shaft on the opposite side to the bend, and one by the bend on the same side as it. I'll let you know how it goes.


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#3 Barnsey123

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Posted 27 September 2020 - 04:29 AM

A**ebiscuits indeed.  Like your idea.  Biggest problem is trying to prevent the axle from twisting in the vice and laying flat as pressure is applied.  This is not helped by the fact that it seems to be made of several components (not one piece of metal) which makes things doubly hard. See pic below.  May need to heat it up to make it more malleable but worried about warping it completely.  As it stands it's almost useless. 

 

Any metalworkers with tips here?

 

Rao 76/1200 focus wheel axle


#4 Senex Bibax

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Posted 27 September 2020 - 07:01 AM

I've given up trying to straighten mine, I'm looking for a replacement instead.



#5 Barnsey123

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Posted 28 September 2020 - 10:08 AM

I've given up trying to straighten mine, I'm looking for a replacement instead.

I've got mine as straight as I can possibly make it (not perfect but a bit better).  Ideally looking for a dual speed focuser. Let me  know if you find anything.  I'm still looking. 
 




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