Bob's Knobs for Celestron 9.25” SCT A. Knobs for C9.25 f/10 Secondary with Standard Collimation Screw Threads Part: C9.25stdFits: Celestron 9.25” (23.5 cm) f/10 SCT versions with standard collimation screw threads. Not for CPC 925 or C9.25 with “Trifid” Faster or EdgeHD optics (see Items B and C below).Knobs: Black plastic, 16 mm (5/8”) diameterThreads: Black anodized aluminum alloyNotes: Silver factory collimation 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. The factory dust cover will fit normally with Bob’s Knobs installed. Knobs include a set of long spacers so they clear the secondary housing lip. Celestron 9.25” SCTs manufactured prior to 2006 have standard collimation screw threads. B. 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”) diameterThreads: Black oxide or stainless steelNotes: 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. 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. 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. The factory dust cover will fit normally with Bob's Knobs installed. 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. C. Knobs for C9.25 f/10 Secondary with Metric Collimation Screw Threads and “Trifid” Fastar Housing Part: C9.25fstFits: Celestron 9.25” (23.5 cm) f/10 SCT versions with "Trifid" Fastar secondary housing ONLYKnobs: Black plastic, 15 mm (5/8”) diameterThreads: Black oxide steelKnobs with silver screws may come apart if they are over-tightened. We have developed a new design using black screws that have a stronger bond with the knob. If needed, contact us using the link below for free replacement.Notes: These knobs fit only the Celestron 9.25” f/10 SCT with a Fastar secondary which has black Phillips factory collimation screws that are recessed into the secondary housing. These knobs will fit C9.25 Fastar telescopes with or without EdgeHD optics. Collimation screws on these telescopes are small with very fine threads. Knobs must be tightened gently (just enough to hold the secondary in place) to prevent damage to either the knob or secondary assembly. Knobs include a set of long spacers so they sit slightly above the rotary cover opening. The rotary secondary cover must remain open when the knobs are installed. The cover is cosmetic only and will not affect operation of the telescope. The factory dust cover will fit normally with Bob’s Knobs installed.
