Quote:
Originally Posted by bratislav
There is no issues with aberrations even at f/4, unless you do critical high resolution planetary work. Here's a 6mm BK7 plate (same as in AO-L units) at 85mm from focus at 420-700nm .
40 microns of chromatic focal shift may sound like a lot, until we remember that all uber expensive APOs would easily have five times that (or even more)!
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Your insightful analysis has saved me much trouble.
I regularly use AO with an F3.8 system +16803 sensor.
The simple fact is: stars have more intensity and better FWHM's with AO across the entire field, than without AO.
Further with AO any CCD focal-plane tilt often masked by a standard guiding blur circle, becomes obvious with the AO.
As for CA....trivial at best...I've never detect any difference with or without.