Bob's Knobs for Celestron 5" SCT A. Knobs for C5 f/10 Secondary with Standard Collimation Screw ThreadsPart Part: C5stdFits: Celestron 5” (13 cm) f/10 SCT (C5, NexStar 5) with black Allen, silver Allen, or silver Phillips factory collimation screws. These screws have standard threads. Will NOT fit scopes with black Phillips factory collimation screws (see Item B below). Knobs: Black plastic, 13 mm (1/2”) diameterThreads: Black anodized aluminum alloyNotes: These knobs will fit all C5 models made prior to 2006, and all 2006 and later models EXCEPT those with black Phillips factory collimation screws. The black Phillips screw model requires C5 metric knobs (Item B beolw). Check that our screw threads match the factory screw threads before installing. The factory dust cover will fit normally with Bob’s Knobs installed. 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. __________________________________ B. Knobs for C5 f/10 Secondary with Metric Collimation Screw Threads Part: C5metBO (black oxide steel); C5metSS (stainless steel)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 (see Item A above).Knobs: Black oxide steel (black) or stainless steel (silver), 12 mm (1/2”) diameterThreads: Black oxide or stainless steelNotes: 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. 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. 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. The factory dust cover will fit normally with Bob's Knobs installed. 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. __________________________________ C. Knobs for C5 f/6 Secondary with Standard Collimation Screw Threads (rare) Part: C5f6Fits: Celestron 5” (13 cm) f/6 SCT only. Will not fit the Celestron 5” f/10 SCT.Knobs: Black plastic, 13 mm (1/2”) diameterThreads: Black anodized aluminum alloyNotes: These knobs will fit only the rare C5 f/6 telescope. If your secondary looks like this, you have the f/6 version. The factory dust cover will fit normally with Bob’s Knobs installed.
