Newtonian R&P Focuser drawtube loose, rocking back and forth.

[Conor Casey]

Hello,

I was hoping that someone here would be able to point me in the right direction. I have a Skywatcher 1145p Newtonian (picture below). It has a fairly simple rack and pinion focuser. I have noticed that there is a lot of play in it. When focusing I need to keep a finger on it as it rocks up and down when focusing the draw tube in and out. It cannot hold large eyepieces or a camera at all and when putting in a laser colimator I can move the laser all over the place with the movement in the draw tube.

My question is how do I tighten it up. The previous owner gave me some nylon shims and there are a couple in the draw tube already. I can't see any Allen keys that could tighten up the mechanism. Is there a way to make this mechanism more solid? I searched the forum but couldn't find anything, google has given me results for Crawfords and R&P focusers that have tension screws. I could be wording this question wrong to be honest, any help would be much appreciated.

 

- Conor

[Louis D]

Low cost R&P focusers generally don't have any adjustment mechanism(s) to reduce the wobble you're experiencing.  Shimming the tube is generally the best workaround short of upgrading the focuser.

[bobro]

Adhesive PTFE (Teflon) strips along the inside length of the focuser are a useful and low cost way of tightening up holding of the inner tube and therefore eyepieces/cameras. Something like 5mm wide and 0.5mm thickness. The strips stick to each other to increase thickness if necessary. There may already be something similar inside the focuser as an example.

 

Edited August 14, 2020 by bobro