Please help, serious focus issues

doc3170 · Oct 1, 2008

I was out viewing the other night when while pointing my scope (an XT 8 Classic) near the zenith I nearly tipped it over.  After this bump I was no longer able to focus, so I packed up for the night planning to collimate in the morning.  A little inspection showed the spider knobs had vibrated loose.  Man I hate messing with the secondary mirror.  I collimated it this afternoon & took it out tonight, but it still doesn’t focus properly.  Everything looks fine through my 25mm EP, but through all the others stars look like fuzzy doughnuts.  For a nearly perfect example of what it looks like there is a picture in The Backyard Astronomers Guide (Revised Edition) on page 124.  It should be noted that when using the 25mm EP, the focuser is about ¼ of a turn from full travel.  Is this normal?            I think my scope is properly collimated.  I think maybe the bump may have hurt the focuser somehow.  If the focuser would travel a little further, I think it would focus fine.  However, I’m not certain & this isn’t the whole story.              When I got my scope the secondary was completely retracted, probably for safety during shipping.  This being my first experience with collimating, the laser that the scope came with wasn’t useful.  The laser dot pointed to the wall inside the scope.  So I learned to collimate using the collimating cap, it took me about eight hours to figure it out, that includes a few frustration breaks.  Since then I’ve just used the cap, but the only thing needing adjustment since that day was the primary, which is a snap.  After collimating the first time & taking my scope out to see fuzzy doughnut stars, I decided to check it with the laser & sure enough it was out, the dot hit the ceiling.  So I collimated it using the laser, & it’s even worse.  In order to get the laser to return to itself, the secondary is tilted so that there isn’t a complete view (you see the side of the tube).  Also, the same fuzzy doughnut stars.  I also need to mention that the day I got my scope I dropped the laser on the concrete floor in the garage, Ouch!  Because it’s been dropped & the fact that when the laser lines up, you don’t get a full picture, I don’t trust it.  So I re-collimated it using the cap again & tonight the same fuzzy doughnut stars again.              All of that said, I think the scope is collimated properly.  I think either the focuser needs an adjustment of some kind, or when I tightened the spider knobs, it changed the hanging position of the secondary, which might be causing problems.              Any thoughts or ideas you might have would be GREATLY APRECIATED.  Sorry for writing a book, I felt you needed all the info.  Please help me.    Thanks,   Olie <div class="Discussion_UserSignature"> </div>

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Please help, serious focus issues

doc3170

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