This is a post about making a simple collimator for your newtonian/dobsonian telescope. I will not go through the process of telescope collimation which can be found in an excellent article, here. Its easy and it costs nothing. It might not be as cool as a laser collimator but it needs no battery and after some time and with experience you may be able to collimate your telescope perfectly. It’s a method that it already has been described in some forums and books but it harms none to be repeated.
All you need is a film can (tube length is not an issue) and a small knife or scissors. Open a small hole (3-4mm) to the center of cap’s can. It usually is marked already so you’ll not have to make any geometrical calculations for that. You also need to cut the bottom part of the cap. So why a film can? Because it has the diameter of an eyepiece (1 1/4in-3cm) so it fits nice on your focuser.
(Optional) If you want, theres an option to make your handmade collimator, cross haired. You ll be able to “target” the center of your mirror that way and you ll minimize the effort of collimation. Thats easy too! You just have to calculate the points of the circle where you ll place the threads. I have made a small drawing to show you the way. All you need to do is to draw circles of the same radius, centered in the perimeter of your main circle(film can). See the 4 x’s ? All you need to do, is to find the middle point of the distance between them(in pairs). There’s another way, like drawing more circles around until you have something like a starry cross in your circle(that’s easy too-if you want it just drop me a comment) but i was in a hurry and i made it as in the photo (took me some seconds to draw that). When you have found the magic spots just make 4 small cuts and place in them, 2 small pieces of thread.
Thats all! Just saved yourself 20-50 USD or euro. Soon, i ll upload full plans of a Cheshire collimation tool.