Celestron C14 focus rod unscrews rather thhan moving mirror up an
Celestron recently did a cleaning on my c.1980 C14 but someone forgot to put any padding in the trunk when they shipped it back. It bounced around roughly in the trunk. The focuser now unscrews outward rather than moving the mirror and collar up and down the central baffle. What do I do to free it and get the scope working again? I do not want to take the corrector lens off...
Re: Celestron C14 focus rod unscrews rather thhan moving...
Hi starHome: Looks like someone will have to remove the corrector plate and the rear cell to get to the focus bar on the primary mirror.once apart, then we will have more information to work with. SHT55
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The Celestron manual for this scope has nothing to say, but on the underside of the focuser assembly, between the 2 focus knobs, you may see 2 screws. They might be thumbscrews or some other screwhead type. One is the adjustment for the focuser internal clearance, or looseness, and the other is a focus travel lock. If present, try backing both off 1/2 turn from tightness, and then experiment to see which is which. The focus lock will have no effect until tight, when the focuser will cease moving, as is now. The other screw will gradually remove looseness and rattle from the focuser until it just moves smoothly, with no back and forth loose feeling at the knob. If neither of these screws is visible you will have to take it to a binocular and telescope shop, where they should not charge much.
The focus knob turns on a threaded rod which passes through a focus lever, which is secured to the back of the primary mirror. The end of the rod where it passes through this lever is secured by 2 jam nuts, one of which has probably fallen off. http://ngc1514.com/Celestron/disassem.htm
To fix this you will have to take the front corrector plate off, find the nut rattling around in there, and tighten it back onto the end of the focuser rod, as shown in the diagram. I'd use a little Loctite as well. This is not difficult, and you can clean the inside of the corrector plate while you have it off. The only precaution is to mark where the corrector plate was, and replace it at the same orientation. Some opinion has it as being worthwhile to also get the secondary mirror centered on the corrector, and the corrector then centered in the end casting. An accurate rule or vernier calipers can be used. Don't tighten the screws on the corrector plate retaining ring much more than hand tight. http://www.astromart.com/articles/article.asp?article_id=594
I think the threaded shaft of the focuser has come right out of the hole in the focusing lever which attaches to the back of the mirror assembly. It should have a stop nut and jam nut at the end of the screw shaft which can be seen in this diagram http://ngc1514.com/Celestron/disassem.htm
The focus knob is not supposed to feel like that. On my Celestron it had almost become detached from the focus lever which attaches to the main mirror inside the tube. There is a threaded shaft and locknut which had become loose.
If you feel DIY enough, and you understand about corrector plate centering, follow this
Did you ever see any "light" how about something that looks like a donut with a hole in it?
The focus know could have come loose from the "rod" inside that moves the mirror. OR the finder scope really is NOT lined up exactly with the main tube.
Take the telescope out during the day and see if you can focus on a distant object like the top of a telephone pole. If you can focus just fine, then the finder scope is NOT lined up with the view in the eyepiece. Also try using a lower power eyepiece -- anything over about 22mm to get a wider field of view.
The C8 optical tube has a very large focal range. It should be capable of focusing on objects from 15' to infinity. To focus on object at infinity you have to move the primary mirror foward. You do this by rotating the focus knob CCW. Rotate the knob CCW until it comes toa stop them slowly bring the mirror back by rotating the knob CW while viewing the object. It will snap to focus so don't move too fast yor you'll miss it.