Eyepieces won't come to focus

Started by Ed Ashton, 11/30/2005 09:00PM
Posted 11/30/2005 09:00PM Opening Post
I picked up a used Starmaster 11" ELT F/5.4 a while ago, but never got around to using it until recently. My problem is that none of my eyepieces will come to focus....not one! I don't have any 2" eyepieces, so I used my Televue 1.25" adapter, which raises the eyepices maybe a quarter of an inch, but I cannot get enough in-focus travel to bring even short eyepieces to focus. Is there any simple fix for this? Would a binoviewer OCS do the trick? Any other suggestions?
Posted 11/30/2005 09:10PM #1
If you know it's in focus that's required you may be able to fix this with the collimation adjustment. Using your collimation knobs, raise the mirror so it move closer to the secondary. You may be able to move the mirror close to an inch. Re-collimate and try again.

Gary Weber
Posted 11/30/2005 09:31PM #2
When I got a 2" barlow for my 12" HOC I had to move the mirror up so that EPs would focus. As noted previously you might have enough movement in your mirror to rectify the problem. But, I had to reinforce the springs because they did not have enough tension to hold the mirror mount in place without the stabilizing screws tightened, which made it tough to collimate. hopefully you will not have that problem.

I Yam What I Yam!
Posted 11/30/2005 10:04PM #3
Hey Ed,
This does not seem right for an ELT. You might call Rick and ask about it.
What focuser does it have, a Rack and Pinion or Crayford type? Any type of spacer block under the focuser that could be removed?

[SIZE="Large"][/SIZE][COLOR="Blue"][/COLOR] Floyd Blue grin
Amateur Imager
Posted 12/01/2005 12:26AM #4
It might be the Televue 1.25" adapter. I have a couple of these and they will raise the eyepiece, making the eyepiece farther from the mirror. Get a flat 1.25" adapter that will lower the eyepiece. That extra 1/4" to 1/2" will give your eyepiece more in travel and should allow your eyepieces to come to focus.
Posted 12/01/2005 01:38AM | Edited 12/01/2005 01:39AM #5
Hi Ed
I have the same SM11" F/5.4 and have no problems with any of my eyepieces (mostly TV). Do you have the JMI focuser? Try holding an eyepiece up to the focuser without the adapter and see if you can move it in enough to get focused, it may not look good but you should be able to tell. My guess is that you have the TV highhat adapter and you will probably need the flattop. That 1/4" will make all the difference.
Hope this helps
Buck