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Re: I Camera Flatness
To answer the question, "How flat is the field of a camera",
I look at the mean value of the blank sky near the center,
and the mean value of the blank sky near the corners. I then
(central - corner)
non-flatness = ---------------------
The images in TN 76 show that the worst spots by far are
the very corners of the image, in the area outside the
lens design. That makes sense.
In the case of the I-band images in Data Disk 16, I find
center of image ~ 3120 ADU
center of worst edge ~ 2950 ADU 5 percent
best corner ~ 2750 ADU 12
worst corner ~ 2550 ADU 18
The field _is_ much better than ordinary lenses, that's for sure!
I'm not criticizing anyone.