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Old 29-05-2018, 07:48 AM
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Atmos (Colin)
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Join Date: Aug 2011
Location: Melbourne
Posts: 6,425
Mewlon 250-S CR back focus

I bought a second hand Mewlon 250-S late last year and I came with a corrector which currently isnít installed. Iím planning on doing some high resolution imaging with it and cannot quite figure out where the back focus is calculated from.

What Iíve found is below:
Metal back distance** 115.5mm


** Optimum imaging BACK FOCUS as measured from the rearmost surface of the optical device used that will make contact with the next adapter in the imaging train. [This is a critical distance for optimum imaging]

Considering how accurate the back focus needs to be, does anyone how where this 115.5mm is calculated from?
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