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Collimation Again, Again, Again



 
 
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  #1  
Old April 29th 04, 02:44 PM
Robert Geake
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Default Collimation Again, Again, Again

Chaps,

Having now put my mirror right out and back about a thousand times
i think i can say i know how to collimate it. One question i have means
explaining my checking proccess:

Pick a bright star and put it so far out of focus that i fill almost the
whole
view. If the spyder is central in the brighter area of the view collimation
is
correct....

Does anyone think this sounds about right?

Rob


  #2  
Old April 29th 04, 06:29 PM
Tim Auton
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Default

"Robert Geake" wrote:

Having now put my mirror right out and back about a thousand times
i think i can say i know how to collimate it. One question i have means
explaining my checking proccess:

Pick a bright star and put it so far out of focus that i fill almost the
whole
view. If the spyder is central in the brighter area of the view collimation
is
correct....

Does anyone think this sounds about right?


Sounds about right, but a bit imprecise. I've found slight defocussing
at the highest magnification you can (to see the airy disk and rings)
is more precise - I think that's what is usually meant when "star
testing" is referred to.


Tim
--
Love is a travelator.
  #3  
Old April 30th 04, 09:33 AM
Robert Geake
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Default

Tim,

Never really understood what im looking for in a star test.
I get very good planetary/faint fluffie views but point
sources(stars), im guessing thats cos of the diffraction
caused by the spyder.

Rob


"Tim Auton" tim.auton@uton.[groupSexWithoutTheY] wrote in message
...
"Robert Geake" wrote:

Having now put my mirror right out and back about a thousand times
i think i can say i know how to collimate it. One question i have means
explaining my checking proccess:

Pick a bright star and put it so far out of focus that i fill almost the
whole
view. If the spyder is central in the brighter area of the view

collimation
is
correct....

Does anyone think this sounds about right?


Sounds about right, but a bit imprecise. I've found slight defocussing
at the highest magnification you can (to see the airy disk and rings)
is more precise - I think that's what is usually meant when "star
testing" is referred to.


Tim
--
Love is a travelator.



  #4  
Old April 30th 04, 07:32 PM
mike ring
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Default

"Robert Geake" wrote in
:

Tim,

Never really understood what im looking for in a star test.
I get very good planetary/faint fluffie views but point
sources(stars), im guessing thats cos of the diffraction
caused by the spyder.

Rob

Have a look at this, Rob

http://perso.club-internet.fr/legault/collim.html

I didn't respond to your first post because I've mentioned it before,
but WTH, I'll only get shouted at.

It showed me I needed to take it in stages, and you can't move on until
you've done the previous stage as the gross errors have to be cleared
before you can see the subtle ones.

It's helped me a lot, specially when I suddenly saw a whole specckled
effect of very faint stars that (even thogh I couldn't quite see them)
weren't even there before.

And now my planetary views are much sharper.

There's also physical collimation, which is lining up all the bits
BEFORE you try to center the optical axis of the mirror down the centre
of the tube.

So there's another oreference here

http://zebu.uoregon.edu/~mbartels/kolli/kolli.html

HTH

mike r
 




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