My impression from memory and visual testing
is that the TMB 80/600 has slightly less CA than
the Vixen 102/920, but both are really very nice.
The difference is a matter of splitting hairs.
Regarding spherical and astigmatism, etc., I will attach
some Roddier test results for a Vixen indicating minimal
aberrations and Strehl 98%. I've seen several of these and
the related Celestron C102F that were very close in
performance to this one -- all had spherical better
than 1/10 wave PTV and undetectable astigmatism. None
was significantly worse. Some have very low-level
trefoil or similar aberrations -- like a pinch but
in the glass -- some sort of glass melt or uniformity
issue, but at extremely low level like 0.03 to 0.05
wave PTV.
As regards the TMB, I think you could order
whatever Strehl ratio and level of aberration you
wanted. One I tested in a similar fashion had
Strehl 99%. But I am not sure what the average
Strehl ratio would be, or what the range of values was.
Which to own? The 4" scope will show more detail on
planets. The 80mm triplet might be better for imaging
-- I am guessing it probably has better CA far in the
red and in the violet -- where the eye is not so
sensitive but detectors are.
Attached Image:
