Collimating Newtonian reflector telescopes can be a daunting task, but it is crucial to achieving good performance, especially for those instruments with fast focal ratios (eg., f/5 and less).
This tool uses a red laser of adjustable brightness, and employs a view port so as to see just how far off axis the return beam lies. It allows for precise alignment of both the primary and secondary mirrors, albeit with a caveat for secondaries (more below). It fits standard 1.25" focusers, and the included 2" reducer adapter permits fitment to those larger focuser receptacles.
Step One - Secondary Mirror Tilt - Send the laser spot to the primary's center spot, by adjusting the secondary mirror tilt screws.
Step Two - Primary Mirror Tilt - Send the return beam back through the small opening in the view port, by adjusting the primary mirror tilt screws.
Step Three - Collimation on a Star - A final star collimation should be performed to weed out any residual error. For telescopes that don't track, use Polaris because it barely moves.
Aren't Laser Collimators the Best? - Not necessarily. Particularly if one has not verified that the secondary is properly positioned under the focuser (which the Cheshire type device does.) It's difficult to ensure that the laser is hitting the
of the secondary, especially considering that most reflectors don't allow for direct observation of the secondary mirror reflective surface while the laser is installed. Experts advise customers using laser collimators to place a centre mark on their secondary mirrors, and over the last couple of decades we've only seen a small handful of customers willing to do this.
Laser collimators with a side-viewing inspection window are useful when collimating primary mirrors, especially of longer focal length instruments, because you can see your adjustments in real-time. Follow it up with the Cheshire, if you have one, to refine your alignment.