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Bob's Knobs Celestron 6" SCT

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Bob's Knobs
$33 CAD

We will price-match in-stock Canadian astronomy dealer pricing


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The knobs below will fit almost all versions of the Celestron 6” Schmidt-Cassegrain secondary. Price is for a complete set of knobs.

IMPORTANT NOTE: Secondary collimation screws have threads (measured below the screw head) that are either 10 mm or 12 mm long. We include a set of white spacers to be used on the knobs if factory threads are 10 mm long. Do NOT use the white spacers if the factory screw threads are 12 mm long.

Knobs for C6 f/10 Secondary with Metric Collimation Screw Threads

This set of 3 knobs will fit all versions of the Celestron 6” Schmidt-Cassegrain secondary.

Part: C6BO (black oxide steel); C6SS (stainless steel)

Fits: Celestron 6” (15 cm) f/10 SCT versions (C6-A-XLT, C6-GT, C6-S, C6-SE, C6-SGT, others)

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


  1. All versions of the Celestron C6 SCT have collimation screws with metric threads.
  2. Black oxide steel (shown in photo) is for dry environments. Lightly oil the knob top and knob serrations periodically as an anti-corrosion measure. Stainless steel provides better corrosion protection in coastal or high humidity areas, or in places where dew or other condensation is common.
  3. The factory dust cover will usually fit properly with Bob’s Knobs installed, except on some very early versions.

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