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How to collimate a Newtonian telescope - BBC Sky at Night Magazine
A Beginner's Guide to Collimation - Gary Seronik
Astromania 1.25Inch Metal Collimating Cheshire Eyepiece without Laser for Newtonian Reflector Telescope - Short Version: Telescope Accessories: Amazon.com.au
Collimating a Newtonian Reflector - basics for beginners