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The collimation of an SCT can be a daunting task for a beginner, but it is an absolutely necessary process to get the most out of your telescope! Doing the collimation with the factory Phillips screws is certainly doable, but requires a lot of back and forth between the eyepiece and the secondary mirror. You also need to work, in the dark, close to the corrector plate with a sharp metal screwdriver, requiring a lot of concentration and precision in your movements.

By replacing the factory Phillips collimation screws of your Celestron 5" with a set of Bob's Knobs collimation thumbscrew, you can make the process of collimation an effortless and risk-free task. Simply grab a Bob's Knobs thumbscrew and turn!

The factory dust cover will usually fit properly with Bob’s Knobs installed, except on some very early versions.

Fits: Celestron 5” (13 cm) f/10 SCT (C5, NexStar 5SE, Omni 127) with black Phillips factory collimation screws. These screws have metric threads. Will NOT fit scopes with silver factory collimation screws.

Knobs: Black oxide steel (black) or stainless steel (silver), 12 mm (1/2”) diameter

Threads: Black oxide or stainless steel.

Due to the Canadian weather, we, David Astro, decided to only offer the slightly more expensive, but more durable stainless steel Bob's Knobs.

  1. These knobs will fit only 2006 and later C5 models that have black Phillips factory collimation screws. All C5 models made prior to 2006 and all post-2006 models with black Allen or silver factory collimation screws require C5 standard knobs (Item A above). Check that our screw threads match the factory screw threads before installing.
  2. Some C5 scopes have metric collimation screws that are 10mm long rather than the more common 8mm. If your secondary looks like this, you have screws with 10mm thread length and you should install knobs without the white spacers.
  3. The factory dust cover will fit normally with Bob's Knobs installed.
  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.