How tight should the knobs be?
After adjusting collimation, the knobs should be neither “too tight” nor “too loose.” There is often less than one knob turn between these two extremes, especially on smaller telescopes. A knob is too tight when there’s a marked increase in effort to turn it. Also, the extra tension on the secondary mirror mounting plate may cause optical aberrations to appear. Forcing a knob even tighter may damage either the knob or the secondary mirror assembly. A knob is too loose when the secondary mirror assembly rattles when a knob is wiggled. A telescope will not hold its collimation when the knobs are loose. After installing Bob’s Knobs, you can easily determine the range between “too tight” and “too loose” by experimenting with them prior to performing the coarse collimation. Once all three knobs have the correct tension, collimation is achieved by tightening and loosening different knobs while keeping all three within the correct tension range.
