I suspect someone has knocked over my telescope and damaged it. When I try to focus, I turn the knob but nothing moves, the knob just turns and turns. What has happened and what can I do to fix it?
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.
I just experienced the same issue with the focus knob. Endless rotation but no movement on the shaft. I then followed Geoff's suggestion and ended up removing the focus knob assembly all together. When you remove the couple of Phillip head screws then it detaches. There is a gear axle that was not contracting with the gear tooth's on the shaft. The shaft was too far into the tube. I moved the shaft just enough so the shifter knob axle can be in touch with the gear tooth's on the shaft and the problem was solved. Not very strongly build or designed though in my humble opinion. Thanks.
SOURCE: Focus knob screw
I've had the same problem. Unfortunately, these are knock-off scopes. If the shaft that the focusing knobs attach to is still there, you can replace the knobs themselves by ordering THIS part. If the shaft AND the knobs are both missing, you'll have to replace the entire focusing mechanism (sorry, but I don't know where to order the housing from). Hope it's more helpful than the prior answer.
SOURCE: Cannot see anything out of main telescope
Do NOT use the barlow lens-- put the lowest magnification eyepiece into the scope-- practice focusing on the moon -- turn the focus knob slowly in and out until you get a sharp image.
Telescopes only show an area of sky about 1 degree wide or LESS--- this is about the size of the TIP of your finger held at arms length................ your scope is best used at low magnification.
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What model of Celestron?
Its the Astromaster 70
Thank you Geoff for the suggestion. I tried loosening these screws as you described but nothing happened. The focuser appears to be stuck fast in the forward position. I'm even thinking that it is further forward than it should be. (can't find a suitable photo to check against) I suppose I'm going to have to take it to a shop to get it looked at. Unless you have any other suggestions. Thanks again for your input.
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