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Captain Magenta

Laser Collimator

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I recenty acquired, courtesy of a fellow forumite, a Howie Glatter laser collimator, the combination 2"/1.25" 625nm one. It's a real lump.

Having read that one needs to be very sure that any such collimator needs to be itself well-collimated, I decided to test mine out over the weekend.

I set up my SkyTee2 mount with one of the ADM saddles at a slightly tilted-over angle to form a reasonably solid "V" for the collimator barrel to rest in. I then set up a target A4 piece of paper taped to a wheelie bin around 25-30 metres away up the garden. I rotated the collimator around and made a series of marks where mid-beam struck the paper. I ended up walking up and down the garden a good few times!

The result: a non-collimation radius of around 3mm at, say, 26 metres distance, giving a self-collimation error of around 24 arcseconds.

I reckon that should be good enough for scope collimation? Has anyone done anything similar for any other brands?

Cheers, Magnus

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Posted (edited)

That is good enough. Once you start adjusting from that level you will walk several kilometres and discover why you should have left it alone.

On a more serious note I am sure I have read somewhere what HG collimate to at the factory. If I find it I will post a reply.

15 arc seconds is the factory setting

Edited by Tomatobro
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the error circle was a bit noisy, so I imagine my 24 arcseconds also included the mounting instability error of my cobbled-together set-up

Even 24 arcsecs though only represents 0.3-0.4mm of error over 2x focal length of a 1500mm reflector...

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An engineers Vee block is great for this. They can be got second hand from ebay.

 

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Or a lathe can be really usefull. Clamp the laser in the chuck and shine the laser through the headstock. 

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