Back in the Saddle….so to speak!

December 30 2013

Wow, its been 11 months since I last did any real astronomy or astrophotography. The past 11 months have been difficult due to weather, motivation and life in general.

Anyway, I have decided that 2014 is going to start off on the right note and to get myself going I am starting with the age old job - collimation. 

But, not collimation of a conventional scope, rather my AstroTrac (AT) Polarscope. To help others I have decided to document the process in one place.

So how do you collimate the polar scope of an AT and what do you need to do?

Collimation is two fold. Firstly, we need to make sure that the polarscope reticule is centred, secondly we need to make sure the polar scope arm rotates, centrally, about the AT.

Step One - Polarscope Reticule Centring

The initial step is to ensure that the polar scope is centred about its own axis.

To do this you need to first set up your AT and aim the polarscope on a distant object such as a pylon, telegraph pole or any other distant, stationary object

Once you have chosen your object align your polar scope so that the centre (the intersection of all markings) is aligned to the top, or other definable point, of your object. Once aligned you can rotate your polarscope through 360 degrees. A correctly collimated or centred polar scope will keep its place when rotated. If your polar scope is badly collimated you will see the centre move around and off your definable point as you rotate.

I chose a distant radio mast with a conveniently placed light ontop. The following set of photos show how the light is covered, but then emerges as I rotate the polar scope around through 360 degrees:

This clearly shows that the polar scope is in need of collimation.

Here is where the fun begins!

To collimate the scope you need to adjust the 3no grub screws that are located around the barrel near where the illuminator sits:

To help with the adjustment I have ordered some 3mm thumbscrews to replace the grub screws used.

I currently have them on order from here:

Now I just have to wait to see if they are long enough......

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