Fitting Bob’s Knobs on my SCT …. Collimation is the alignment of optics in your telescope. If your mirrors aren’t aligned, light can not be accurately focused. Unfortunately carrying your scope around a lot can move mirrors out of place, and just like a musical instrument needs to be in tune to play properly – your mirrors need to be aligned to see/photograph properly.
My Celestron 11”SCT has a secondary mirror in the front of the OTA (Optical Tube Assembly). The secondary mirror housing is secured by 3 Phillips screws. To adjust the angle of the mirror any one (two or three) of the screws need to be adjusted ever so slightly to get proper alignment of the mirror. Problem is doing this in the dark, with a screw driver – so close to the corrector glass, dangerous!
Thankfully Bob was smart enough to put some thumbscrews together to make the process easier. [Bob’s Knobs they are available for most telescopes]
It’s pretty simple to fit them. All you do is remove the original screws and replace them with the thumbscrews one by one. Simple… (It is very important that you read the supporting documentation on his site to ensure you order the correct screws for your scope) Note that it’s not ‘impossible’ for your secondary mirror to fall out should you do this wrong. So – best take care and do it right.
And that’s it…
Thumbscrews make collimating really simple. You can view and adjust simultaneously which speeds up a tedious process.
Want to find out more how to collimate your SCT?