Collimate your Catadioptric or Newtonian reflector style telescopes without tools!
It's easy...just grab a Bob's Knob collimation thumbscrew and turn. You can even do it while looking through the eyepiece on most scopes. These thumbscrews are also much easier to use with gloves on. And perhaps most importantly, you'll never drop that pesky little Allen wrench or screwdriver into the grass again. Installation is a snap with the included instructions, and you can undo the modification at any time.
Fits: Celestron 8" (20 cm) f/10 post-1980 SCT with factory Allen or silver Phillips collimation screws, with or without Fastar secondary with silver collimation screws (C8 black, or gray; Ultima 2000; NexStar 8; others). This includes the post-2000 orange-tube. Will not fit pre-1980 orange tube or most scopes with black Phillips factory collimation screws.
Knobs: Black plastic, 13 mm (1/2") diameter
Threads: Black anodized aluminum alloy
1. These knobs will fit C8 models made prior to 2005 (except pre-1980 orange tube), and most post-2005 models with silver factory collimation screws.
2. Most models with black Phillips factory collimation screws require C8 metric knobs (Item C below) A few post-2005 scopes have black Phillips collimation screws with standard threads. Here are some hints to help determine which screws your telescope has. Make sure the knob threads match the factory screw threads before installing the knobs. More information is in our Celestron Technical Paper.
3. We provide spacers to raise the knobs slightly for easier use, but the spacers can be omitted if the knobs contact the inside of the full-aperture dust cover. Spacers are required for knobs installed on the Fastar secondary with silver collimation screws for proper clearance.
4. Some telescope versions have a small plastic cover over the factory collimation screws. This cover must be removed and set aside when Bob's Knobs are installed. The cover is cosmetic only and will not affect operation of the scope.