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Telescope fine focus slipping


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I have a WO FLT120 telescope which features a 3.3" R&P focuser with a 1:10 fine focuser. I've encountered a bit of a design flaw where there's some slippage with the fine focuser for the inwards travel of the focuser. I've linked to another thread below where I've describe this issue specific for the FLT120 so the purpose of this thread is to ask for general advice for other telescopes/focusers.

In a nutshell, the fine focus shaft does not have a flat section, so when you tighten the grub screw for the focus knob/auto focus adapter, then the knob/auto focus adapter can sometimes freely rotate whilst the fine focus shaft stays still. 

I'm wondering if anyone else has had this type of issue with any other type of focuser and what you've done to resolve it? I'm thinking that filing a small flat section to the shaft should do the trick but I'm going to contact the vendor first as this is still under warranty and I don't want to permanently alter something as a first course of action. 

 

 

Brass colour is coarse focus shaft (notice the flat spot). Silver shaft is fine focuser (no flat at all). 

20220216_185520.thumb.jpg.99d2245d8aedd87abde47470ebe09419.jpg

 

Black adapter is for autofocuser, notice the silver grub screws which contact the fine focus shaft. 

20220216_190416.thumb.jpg.6f2c968e74980204e33ad2766a14b177.jpg

 

Coarse knob attached to coarse focus shaft (Notice the grub screw access hole at top left which results in screw contacting the flat portion of the focus shaft) 

20220216_185446.thumb.jpg.1d63a8a2bbd8084aaff46965ae7af145.jpg

 

Fine focus knob attached (one grub screw which would contact the round portion of the focus shaft, no flat spot to bottom out on) 

20220216_185409.thumb.jpg.4d5e2af3e3ff7b4234e9f6f8e5ce6c71.jpg

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