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Older C-8 focus shift

Started by Brisley, 11/17/2003 07:14PM
Posted 11/17/2003 07:14PM Opening Post
My 1980 C-8 (which had been sitting boxed up for about 6-8 years) had a real problem with focus shift. I removed the primary (I am quite familiar with disassembly, but it is not for the faint of heart!) and applied some fishing real lube to the focus tube shaft where the mirror holder is normally positioned and spread it around evenly. (Shaft/focus bearing assembly had plenty of lube, so I didn't add any.) I checked the assembly first and could find no hint of any lubrication in this area before I added some. After reassembly, there is very little shift. (500x during collimation would sometimes shift the image out of the view, now it stays almost exactly in place!)
Time will tell if this is a good lube to use, unless someone else knows of something better, it really fixed things up for me!
If you are experiencing big shifts, then this is a definite area that may need to be checked. Some people mention releasing the bearing and moving the assembly around in the tube, but I found no lube to be present, so this may not work! This makes my collimation and planetary observing much easier. Weather hasn't cooperated for me to do final collimation steps on a planet, been too unstable here in SW FLA.

Posted 11/17/2003 11:25PM #1
When I asked Celestron about mirror shift they talked of lubing the tube. They did not say what they used however.
I would think that the fishing reel lube would be pretty good stuff really.
Floyd

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