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Extra info that I thought may be of some assistance to potential purchasers.
In talking to John (Ausastronomer) and other people it would appear that matching field curvature of eyepiece to field curvature of telescope is important.
I have tested the Uwan 28 in Tak 130 (thanks Rocket Boy) and Discovery 12.5 Dob (thanks Wavelandscott), the results - hardly any curvature at all. I would say that the eyepiece has in fact flat focal plane (this is on the assumption that the TAK has very flat focal plane as well).
I have not yet seen 70+ deg eyepiece (FL >14 mm) that does not show a field curvature in my 8" LX-90.
I know for sure that the Uwan does not work well in GSO 10 Dob and its fairly reasonable in my LX90.
It also works well in a large number of Dobs as tested by CN users.
I wish manufacturers (of both telescopes and eyepieces) would publish field curvature plots for their products - why do we have to find it out only after the purchase? Pentax does publish it but I do not read Japanese.
Joe
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