Adjusting screws for the viewfinder of an 8 inch SCT f/10, 6 screws | Bob’s Knobs

Adjusting the focus in the dark with a small screwdriver is tricky, and with a holder with six screws it’s even more fiddly. With Bob’s Knobs on your 8-inch SCT, you replace the screws on the secondary mirror with larger buttons with a ribbed edge. This allows you to adjust the alignment with your fingers even when you can see little.

This version is for 8 inch Schmidt-Cassegrains with f/10, where the secondary holder has six screws. First, count how many screws are on your holder. You can find this type of telescope in the catadioptric telescopes.

Never remove all the screws at the same time, but replace them one by one so that the mirror stays securely in place. Then check the collimation on a bright star at high magnification, or with a Artificial star as training point if the air doesn't cooperate. Small turns are enough.

If your holder has three screws, then you have the set for three screws needed.