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Here’s the procedure I used to fit my Bob’s Knobs, as I was concerned about losing the original collimation, so decided to do this in the day time using a domed cap on a metal pole as a reference.
In the day time, I set my C9.25 up on a workbench, horizontal, pointing through an open doorway so I could focus on a metal pole some 100m away.
I shimmed the OTA until the cap on the pole was more or less centred in a reticule eyepiece that has an adjustable position reticule. I then tweaked the X-Y position of the reticule to centre the cap.
Next, I removed one secondary screw and replaced it by one Bob’s Knob and then returned to the eyepiece to see the effects. I then tweaked that Bob’s Knob to bring the cap of the pole back to the centre.
I repeated this for Bob’s Knobs 2 & 3, one at a time, thus retaining the original collimation. On the next clear night, I touched up the collimation using the star test.
Cheers
Dennis
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