Play in focuser (1 Viewer)

Hi,

(Maybe I should direct this question to the retail service where I purchased my scope. Anyhow before doing so I guess some of you may have experienced the same symptoms and can guide me if this can be remedied with the appropriate tools.)

The focuser is a Crayfoord focuser, the single speed design. It shows clear signs of play as it is extended. Fully extended I would say 1-2 mm, assessed at the camera end, mounted on a 80 mm extension tube. The play is also clearly visible where the focuser meets the OTA, a few 1/10 mm. When retracted there is some play but just a fraction of when extended.

When I got the scope (new) the focuser showed no signs of play at all.

I have not dropped the scope or exercised any stress on the focuser, except the torque caused by the camera.

Anyone experienced similar behavior? Is this "normal wear" that calls for adjustment, and can I do it myself? Or do I need to send in the scope to a workshop?

Thanks
/Tord

This should be a simple adjustment Tord.

Turn the scope over and there should be three allen grub screws running in a line under the spindle between the focuser handles. If it's the same as mine the larger middle one will tension the focuser and that should take out some or all of the slack. The two smaller ones either side maybe could do with a quarter or half turn with an allen key just to nip them up. See if that works.

I did mine a couple of weeks ago and I probably do it every few months to get the slack out of the focuser.

Paul.

If you find eventually that you want to upgrade your focuser I suggest that you look at the new linear bearing crayford focusers. I recently purchased the GSO linear bearing dual speed focuser and have been quite pleased with its performance. I believe Baader also sells a similar design though a bit pricier. In this design the draw tube is locked into a stainless linear bearing so there is no slop when the tube is extended--everything else works the same as the normal crayford would. A wonderful thing! Rich

I have the dual knob focuser and it was slipping in the last centimeters when opening it fully.

Since I wanted to have the dual speed knobs on the left hand side, I disassembled it and switched it around. After doing this, I adjusted the 3 Allen screws described by Paul and there was no more play.

Also, be careful with the big knob adjustment. I adjust it to be barely touching the sliding plate. I believe it is there to counter the weight of the camera and to block the focuser if needed.

Paul Corfield said:

This should be a simple adjustment Tord.

Turn the scope over and there should be three allen grub screws running in a line under the spindle between the focuser handles. If it's the same as mine the larger middle one will tension the focuser and that should take out some or all of the slack. The two smaller ones either side maybe could do with a quarter or half turn with an allen key just to nip them up. See if that works.

I did mine a couple of weeks ago and I probably do it every few months to get the slack out of the focuser.

Paul.

Click to expand...

Thanks Paul,

My focuser has one allen grub screw only, though. Tightening it about 15 degrees did the trick, play is now gone.

/Tord