Mnemovore

Diy newtonian collimation tool

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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.

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Written by aperturefever

February 21, 2009 at 3:33 pm

3 Responses

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  1. Just passing by.Btw, you website have great content!

    ______________________________
    Don’t pay for your electricity any longer…
    Instead, the power company will pay YOU!

    Mike

    March 2, 2009 at 7:36 pm

  2. Nice. It’s very interesting. I built myself the film can collimator, but I did only employ to align the mirrors in day-light. I wonder if the film can collimator could be used in the star test, to acquire more precision.

    I have also read about the cross haired and I saw your drawing. Nevertheless I don’t get the point. How do you apply the cross haired to the film can collimator?

    Thanks in advance!

    computerphysicslab

    May 5, 2009 at 10:16 am

    • Hi!
      When im trying to collimate my dob at night i usually aim for distant light bulbs but i agree star testing would provide more precision. At least i do this for binoculars. As for the cross hair you ll need to find a way(glue or small cuts) to place white thread in the points provided by the drawing. The best bet would be to add another film can in the bottom part to make the tube longer (thus easier to focus on the thread) and then making the cuts and stick the white thread in it. At the moment i cant take a pic and upload it but as soon im able, i will let you know. If you want take a look at Nils Olof’s page -> http://web.telia.com/~u41105032/kolli/kolli.html He provides a way to put double thread series in each axis for better precision,

      Btw i really like your blog

      aperturefever

      May 5, 2009 at 11:08 am


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