Bob's Knobs for Vixen VMC200L Catadioptric Secondary

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Bob's Knobs for Vixen VMC200L Catadioptric Secondary

Bob's Knobs for Vixen VMC200L Catadioptric Secondary

Itƒ???????????s easy . . . just grab a Bob's Knob collimation thumbscrew and turn. You can even do it while looking through the eyepiece on most scopes. And you'll never drop that pesky little Allen wrench or screwdriver into the grass again. Installation is a snap with the included instructions, and you can undo the modification at any time.

Note1: Bob's Knobs sit very close to the secondary housing so the factory dust cover should fit fine. However, if the knobs contact the secondary housing before the screws reach the secondary mirror, the manufacturer can supply knobs with longer screws at no charge. If the knobs interfere with the dust cover a shower cap can be used as a substitute cover.

Bob's Knobs Product Number: VMC200SEC


Collimation By ScopeCassegrains
Collimation ToolCollimation Knobs
ManufacturerBob's Knobs
WarrantyLifetime Warranty


Ask a Question
  • After replacing the stock collimation screws with those of Bob's Knobs the dust cover no longer fits. The Bob's Knobs screws protrude out too far even after tightening them to where they feel solid against the secondary mirror cell. What can be done?

    Unfortunately, Vixen never designed the cover for aftermarket collimation screws to be used, and so they do not have a different cover available for this scope. Depending on the diameter of the tube, you may be able to use another manufacturer's cover, b

  • How do I safely remove the Vixen logo sticker/ cover that hides the secondary mirror's collimation screws so that I can replace the stock screws with Bob's Knobs' screws?

    You will need to very carefully use a box cutter or razor blade. The logo is on a plastic pies with an adhesive backing. Tilt the scope slightly downward when you do this so that the piece does not hit the primary mirror when it comes loose.