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Re: [ATM] Ultimate Collimation
It need be no more accurate than the placement
of a center mark would be.
Still I always find this a problem.
Drawing a circle with a compass the same size
as the mirror might be used to do this.
Dropping perpendiculars on the centerline chords
I've always found to be a chore.
marinus van der Lugt wrote:
> Hi John,
>
> > 1) remove reflective coating in center of mirror, about 1/8 inch
>
> You have to be quite sure about the center though.
> Is there a good way to find it?
>
> Rien.
>
>
> On Sep 2, 2007, at 15:26, johncdeitz@comcast.net wrote:
>
>
>> Hello Gang: Try this for the ultimate in Newtonian Collimation-
>> 1) remove reflective coating in center of mirror, about 1/8 inch
>> 2) if mirror cell is solid provide hole through cell at center
>> 3) shine a light at the hole from behind the cell (I use an LED
>> with variable brightness so as to preserve vision- this fits in
>> snug hole at center of the back of mirror)
>> 4) using an autocollimator eyepiece, with the optics roughly
>> aligned, you will typically find two spots of light from the LED
>> (or flashlight etc.). Tweak the mirror to bring these two into one
>> and you will see an additional reflection that is quick to change
>> position- this is very sensitive method! Bring all three head-on
>> and your view is flooded with light as with conventional
>> autocollimator. You will find enough play in the autocollimator
>> that his spot will wink on and off as you play with the
>> autocollimator in the focuser.
>> This method offers the following advantages:
>> 1) you can follow the whole action continuously as the cell is
>> tweaked, unlike with the conventional use of autocollimator
>> 2) can be performed in suboptimal seeing with accurate results
>> 3) no problem with off-set.
>> 4) can be performed without ruing night vision so you will not
>> hesitate to repeat.
>> 5) can even be done by one person!
>> John C. Deitz
>> _______________________________________________
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>>
>>
>
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