2 inch Newtonian reflective telescope collimation cap

thingiverse

Inspired by reflective eyepiece collimation caps, this was my first 3d print design.A 2" telescope collimation cap with reflective material on the face to help create some contrast against the primary mirror centre marker when field checking collimation in low light. The rings were an attempt to make it concentering but it's probably not accurate enough unless you're better than I am at getting the paper/tape cut perfectly round. For people with slower reflector telescopes with properly aligned secondary/primary mirrors, this cap is probably good enough to field check your collimation at night. It won't be accurate enough for "fast" Newtonians, you'll probably need to use a laser or other tools given the collimation tolerance required.There are 3 parts, the cap and two optional rings you can use as templates to help cut paper/tape for the inside and outside rings to try to make it neat. The cutting rings are obviously optional.I used "Cricut" brand glow in the dark sticky paper for mine but anything similar should work OK.INSTRUCTIONSPrint the collimation cap (and optional cutting templates)Either paint the inside of the collimation cap with glow in the dark paint or use some reflective/glow-in-the-dark stick on tape cut to size to make the inside surfaces visible.Use the cap. Hopefully the inside being reflective will help check your primary mirror marks align to the hole in the eyepiece.Enjoy.