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Old 11-05-2021, 07:15 PM
legswilly (Werner)
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legswilly is offline
Join Date: Apr 2021
Location: Wauchope, NSW, Australia
Posts: 47
Originally Posted by multiweb View Post
Any corner in the light path will create diffraction patterns and light scattering. I would not recommend it if your mirror doesn't fit in the shadow of the round holder.

If the secondary mirror is larger then the refection of the primary, then there would not be a corner.

The reason I am trying to find out is that I would like to make a mirror for a autocollimation test stand, the mirror would be a perfectly flat one with a hole in the centre.

To make the mirrors flat, I need 3 pieces of glass. If I am successful and I will try to be, I would have 3 flats and could use one for the autocollimation rig. That leaves me with 2 flats. To cut the oval at a 45deg angle would be more difficult again. So I could use one for a secondary.
If one would get a secondary twice as large as required, would it matter other than the weight and the cost?
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