Focus knob not working

The focus knob is the way you focus overhead projectors. Perhaps you simply haven't turned the knob far enough? How far is the projector from the screen? If it's quite close, you need to turn the knob to raise the lens. If far away, turn it to lower the lens.

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.

1. Power-Cycle your AVerVision Document Camera to reset the focus motor.
2. If your Camera has Auto focus, Press the auto focus button on your document camera's control panel.
3. Reset your camera to Default by Pressing MENU > Default > Yes > Enter. Then Power-Cycle your camera.
4. Check your output device's focus adjustment.
5. Power-Cycle your AVerVision Document Camera to reset the focus motor.
6. If Manual Focus adjustment is available on your camera's remote control, try adjusting back to focal point from the remote.
7. If your camera has a Manual focus knob, manually adjust the focus by turning the focus knob located on the camera head.
8. If adjusting the focus knob does not focus the image, please click here http://support.averusa.com/kb_article.php?ref=9869-UMJQ-1105 for instructions on how to fix the focus ring.

There is a small set-screw near the focuser shaft. Is it tight?

Also you may need to open up the focuser and see if the gears are not stripped.

behind the speaker grill
open up the access panel
look for the focus block - it has 6 knobs, labeled very small and hard to read, r, g, b - focus and screen
-dont move screens unless you need to change the drive of the crts.

there is also a wingnut (mechanical) focus knob on each lens, dont move unless electrical focus doesnt work

There is a central aluminium decal on the focus knob. CAREFULLY prise it off using the tip of a sharp knife trying not to distort it (it's hard to panel beat a small bit aluminium!). Once off you should see a central screw or two screws that hold the focus wheel in place. Remove the screw(s) and the focus wheel noting the orientation of the focus wheel to the body. Use a dot of Liquid Paper to show registration. You can then clean around the focuser and the inside of the focus wheel before reassembly.

Does the focuser move in and out when you turn the knob? If it does then go outside during the day timne and practice focusing on a distant object. Use the eyepiece with the biggest number written on it.

This will give you the lowest magnification-- which is easier to focus.

have repaired a few of these ...some whells have tiny set screws to tighten, some are a two piece wheel that loosens up sometimes, if not that then it is broken. if i can be of further help...15088331232

If there is nothing on the objective lenses or eyepiece lenses then it most likely needs collimation. This is where you adjust the secondary mirror while viewing an out of focus star. You need stable sky conditions to do this.

There are most likely three small screws at the front of the telescope and these are what you use to adjust it. As one screw is loosened then another is tightened. Do this in very small increments. If you have your manual it should outline how to perform this. If not go to this web site: http://www.astrosurf.com/legault/collim.html. It will show examples of how objects look both in and out of collimation. There is a section further down the page for SCTs.

A very handy tool for this is to replace your screws with Bob's Knobs (http://www.bobsknobs.com/) . These replace the screws and allow you to adjust it by hand instead of a screwdriver.

The other focusing problem I've experience with my Celestron SCT is to have the focus knob loosen up and then slip as I turned it so that I could never focus with it.

Good luck and clear skies!

-jodair

The focus knob can have the play reduced. Turn counter-clockwise a turn or 2, then loosen the knob's set-screw and carefully turn clockwise until a little drag is felt. Then tighten the set-screw.
A further item that may pertain to image shift, especially at low powers, is that the baffle tube that the main mirror slides on, may be loose in the back housing. There have been reports of poor thread engagement due to poor tolerences. That tube can be re-tightened - just be careful not to strip the threads!.