Reflector Collimation Knobs
thingiverse
Poor Man's Bob Knobs Make Tool-Less Collimation of Reflector Telescopes Easy. These knobs fit tightly onto 4mm bolts without any tools required. Simply use three bolts to replace the grub screws that came with your telescope, and you're good to go! Just take one bolt to the hardware store and find its exact size. Keep in mind that you'll need extra length because the grub screws are recessed in the secondary holder. My 12-inch Skywatcher dob needed four 35mm bolts. Replace them one at a time to maintain rough collimation.
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