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Old 04-12-2011, 06:33 AM
stevous67 (Steve M)
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stevous67 is offline
 
Join Date: Jul 2008
Location: Melbourne, Australia
Posts: 633
I have been experimenting on various methods to find a simple collmination routine. I agree that a Cheshire will do little for you, even if you give it an icecream.

Over two years I've tried many methods on a RC10" and more recently on a CDK12.5. The choice method has turned out to be a hybrid defocused star routine I come up with (haven't seen it elsewhere). Pointing to an open cluster that reasonably fills your CCD, defocus the image to reveal donuts across your field. These only need to be say 10% the height of your FOV. You'll need at even 4x4 binning a 10 second shot to see these donuts clearly (at F8 say). Having your laptop point at you whilst your at your secondary, adjust the secondary until the centre stars depict nice and centric donuts, whilst the outer most donuts elongate evenly pointing inwards. Once you achieve a nicely spread field of donuts, you will have achieved collimation.

Upon refocusing, any unbalanced flairs or reflections will be the fault of something else (eg, badly aligned primary, secondary not centre, filters not sitting perpendicular to the optical plane, etc).

Using this method takes a lot of the guessing out of which direction to tilt the secondary. Also, conditions don't have to be perfect. Lastly, I can now do it in about 15 mins, possibly you can do it faster with a camera that has USB 2.

Things to remember, when deciding which way to tilt, move defocused stars in the direction of the fat leading edge to get them concentric. Always recenter the open cluster to ensure it stays in the most helpful position.

Steve
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