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DIY focuser Knob

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Hi All,

Just thought I share what I did to my focuser knob, I got the standard R&P skywatcher focuser which is as good as useless sometimes when trying realy hard to get a good focus. So what I did was get a screw on lid from a plastic 5g jerry can, drill a small hole in the middle and screw it in place of the original knob. So simple and so effective. It only clears the OTA by a couple of milimetres but it works.




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Nice fix.

Seen similar mods done with coffee lids etc.


ps: If you ever wanted it done a tad posher, a friendly machinist could also turn you one out of aluminum for a modest sum.

Edited by AndyH
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so the bigger knob allows for smaller adjustments to be made to the focussing?

can i ask why the standard focusser isnt veyr good?

Basically, fine adjustments are very hard as the rack and pinion is too course but by making the knob bigger you can make smaller movements due to circumference differences ie.. a large circumference travela a longer distance thank the smaller knob even though only travelling exactly the same amount of degree's of the original sized knob. I think that's right.


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so its similar if not the same to gears? ie to move the big knob 1 degree requires a bigger movement than 1 degree on the smaller knob, thus allowing greater control

Yes but you put it a bit easyier to understand than I did.

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  • 6 years later...
48 minutes ago, JOC said:

My brother took a cylindrical billet of aluminium and made me this a couple of weeks ago:


He might be up for a commission if anyone wants another one.

That looks brilliant but mine is for a Tal 100rs this is what the knob is like now.




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Having watched the process here I don't think that's beyond doing.  He might be interested in seeing if he could help, but you might need to be in the position of sending down the existing bits and some dimensions.  If you are interested why don't you let me know and I'll send you his email address tomorrow, it will probably be best and more efficient to exchange info with him directly.  If he says he can't help you won't have lost anything, but he is very clever with this sort of thing.  

That one he made for me just skims and misses by thousands of an inch every single protuberance on the telescope.  In fact I was amazed at how difficult it was to actually fit the larger wheel on my system as there were lots of sticking out bits I hadn't noticed before he started.

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