Bob's Knobs for C9.25 f/10 Secondary (non-Fastar) with Metric Collimation Screw Threads

Article number: C9.25metBO
Availability: In stock
Delivery time: In Stock

Knobs for C9.25 f/10 Secondary (non-Fastar) with Metric Collimation Screw Threads

Part: C9.25metBO (black oxide steel); C9.25metSS (stainless steel)
Fits: Celestron 9.25” (23.5 cm) f/10 SCT versions with metric screw threads (CPC 925). Not for C9.25 with “Trifid” Faster or EdgeHD optics (see Item C below).

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


  1. Black Phillips factory collimation screws usually have metric threads, but some black Phillips screws have standard threads. Our hints will help you determine which screws are on your telescope. Make sure the knob threads match the factory screw threads before installing the knobs.
  2. Black oxide steel (shown in photo) is for dry environments. Lightly oil the knobs 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. These knobs sit inside the tall lip around the perimeter of the secondary, so they may be hard to grasp with two fingers. Adjustments can be made using a thumb or finger against the inside edge of the knob.
  4. If your telescope has the “Trifid” Fastar rotary cover, these knobs will not fit. Order Item C below.
  5. The factory dust cover will fit normally with Bob's Knobs installed.
  6. If your telescope has a factory-installed plastic cap over the collimation screws, it 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.
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