Re: Testing old mirrors


 
Edited

Paul, thanks for your letter.
About Gregorian telescopes on the mid. of 18 century - they could be left all spherical and be diffraction limited.
Attached please find a design sample of 2.25" diameter Gregorian telescope by the same master. The data are from Smith's Optics,1738 and it is related to Short's earlier telescopes.
 The second image is a sketch of telescope construction - just for a reference, I have this unit (278/1325 = 9 1/2").
Most of the scopes I have in collection are completed and in working condition. Testing of primary mirrors had a goal to check the shape and appr. quality.
I may consider testing whole telescopes, but it would not be as easy task.
Regards, Yuri

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