Sunday, May 19, 2019

measured AFOV

I just learned how to measure the Apparent Field of View (AFOV) of an eyepiece. It's super-simple!

Set up a rig and tested my 36mm 2" aspheric eyepiece. Quick and crude, I computed the AFOV at 71.2°. baader planetarium says it's 72.

field projection through eyepiece

Do you see the large faint illuminated circle?

We can use the technique to measure the antique ocular at the DDO.


Tip of the beanie to the Cloudy Nights article "eyepiece afov calculation" with discussion, diagrams, and photos as well as the CN article "flashlight test for aperture - illustrated" on using a torch.

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