[mental4astro (Alexander)]

Hi Peter,

I have a similarly modest focuser on an inexpensive scope I have. I too found the draw tube had way too much movement. Modifying it is not difficult to improve its action and reduce this play.

In a nut shell, the hollow in which the draw tube moves through, it is too large, and the spring mechanism that holds the pinion may not be adjusted enough to reduce the play the draw tube has. There are two things you can try.

* First thing to try is to SLOWLY tighten the screws of the tensioner cover plate. It will make the draw tube a little harder to wind in and out, but it may be all you need to do. Do LITTLE, 1/8th turns of one screw, wind the focuser in and out, checking for reduced play, and if not enough, then tighten the other screw a TINY 1/8th of a turn, and repeat this process. Just be careful not to over tighten as this can damage the spring inside the cover plate. The action of the focuser should at most be firm but not stiff.

* Second is doing a modification to the focuser if tightening the tensioner spring is not enough. In this mod, you will need to remove the draw tube from the focuser, and dismantling the tensioner of the pinion so the draw tube can be pulled out. Just keep note of how the tensioner spring is put together when you remove the cover plate so you know how to put it back together. Do all of this with the scope lying flat on a table, NOT on its mount!!!

With the draw tube removed, you place a strip of adhesive backed Teflon tape down the whole length of the draw tube on the side opposite the rack. This tape will provide the necessary filler to reduce the gap between the draw tube and the frame of the focuser. This tape is approx 1/2mm thick, which is plenty enough for this mod.

Replace the draw tube into its frame and reassemble the tensioner assembly. You can carefully tighten the cover plate screws so that the pinion pushes harder against the rack, and hence the draw tube up against the focuser frame. I just needed the one thickness of tape to remove 90% of the play the draw tube had before. The action of the focuser is also a little firmer, but that's OK as it is needed to reduce the play in the focuser.

I'm happy to send you a piece of this Teflon tape is you like. Just tell me how long your draw tube is.

The pic below is a simple diagram on what needs to be done.

I hope this helps,

Alex.