Collimation Of Newtonians

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Collimation Of Newtonians

Postby Dion » Thu Sep 30, 2010 12:38 am

"Very basic" theory of collimation, part 1

This is a very basic rundown of how it all works, if you know how it works, it helps you understand whats going on.

Firstly, take away your secondary mirror and focuser etc, so that all you have, is a metal tube, with a primary mirror at the bottom, the mirror is 'parabolic' (hence the 'p' in a skywatcher 200p telescope) meaning, it's shaped like a satelite dish on it's surface, so, when light hits the primary, it's reflected in a cone shape, like this :-

Image


What you have to understand, is that although it's a cone, getting smaller and smaller as it progresses, it isn't losing any of that light it's collected, it's simply concentrating it into a smaller space, a bit like a magnifying glass and the sun when you burn things, you can do the same with a parabolic mirror, the bit where it comes to a point is the 'focal point' and if you placed a piece of paper or wood at the focal point, and got it in the sun, it would burn the wood/paper, like this :-





So, next we introduce a secondary, now although your secondary is (usually) an oval shape, you only 'really' present a circle to the primary, because it's at 'roughly' 45 degrees. So, the secondary then, reflects the cone to 90 degrees, up your focuser, like this :-

Image


Now, to get the very best image, you want as much of that light to be going into your eye as possible, so, if the primary is out a little, the cone wont be pointing straight at the secondary, so you'll lose some light, if the secondary isn't properly aligned to the primary, again, you'll lose some light, finally, if the secondary isn't ALSO aligned to your focuser, AGAIN you will lose some light.

So

Collimation is the term used for lining up ALL of the three points, focuser, secondary and primary.

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Re: Collimation Of Newtonians

Postby Dion » Sat Oct 09, 2010 11:26 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 9:40 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 10:01 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 10:06 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 10:27 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 10:43 pm

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Re: Collimation Of Newtonians

Postby Dion » Thu Oct 14, 2010 11:07 pm

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Re: Collimation Of Newtonians

Postby Dion » Fri Oct 15, 2010 12:21 am

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Re: Collimation Of Newtonians

Postby Dion » Fri Oct 15, 2010 12:25 am

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