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XX14i doesn't want to stay collimated

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#1 7lx200gps

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Posted 18 November 2012 - 10:48 AM

I've gotten it collimated really well and the other night I collimated it level to the ground and locked down the lock bolts on the back to retain that collimation for that night. When I moved the scope up to the zenith after the let it cool down and wait for darkness, I noticed that when I moved it up it moved off where I collimated it. It was enough to notice star patterns were out of collimation again. Is something wrong? I'm not tightening those lock
anymore than snug, not forcing anything. I can't figure it out. Maybe some of you have have this problem.

#2 mayidunk

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Posted 18 November 2012 - 12:00 PM

IIRC, many recommend that you collimate with the tube elevated to the halfway point (45 degrees), this is what I do with my Sky Watcher Flextube. You might also check that all of the truss tubes are seated properly, and tightened down firmly. You could also check to be sure that the spider vanes are tight enough to keep the secondary from flexing as the OTA is raised and lowered.

I recall recently reading a thread about someone having difficulty with the truss tubes on their Lightbridge moving out of place in the socket when the clamps were tightened down. I'm not saying that this is an issue with the Orion Dobs, but it's one more thing to look at.

#3 Carl Coker

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Posted 18 November 2012 - 08:20 PM

Especially for scopes like the Orions, don't collimate them when they're horizontal. I noticed when I had my XT10 pointed really low, the mirror flopped forward (it stays in the cell because of the clips, but it won't rest on the cell back). Like mayidunk suggested, try collimating it when it's pointed at 45-60 degrees up and see how it goes.

I'll also second mayidunk's suggestion for checking whether the spider bolts are tight. I had that problem before and was mystified why my collimation wasn't holding until I noticed the spider flexing abnormally when I was adjusting the secondary. Tightening the vanes fixed it right up.

#4 soupaman

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Posted 18 November 2012 - 09:36 PM

I would remove the lockdown bolts. In my opinion they're not necessary. I've owned a few Orion and Zhumell dobs and upon receiving them the first thing I do is remove the cell, check the clips, and the integrity of the cell in general. Upon reinstalling the cell I leave the lockdown bolts out. If your collimation continues to shift, replace the springs.

#5 paul hart

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Posted 19 November 2012 - 09:52 PM

I will recommend both previously suggestions of not using/removing the lockdown bolts as they have changed collimation in scopes I have had them in when tightened. Also I recommend collimating at a 45 degree angle. Additionally when collimation changes, I've found quite often I don't have something tightened down. I've found loose secondary mirrors, primary mirror or truss tubes on different occasions.






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