Quote:
Originally Posted by Hans Tucker
The Takahashi FS series refractors seem to produce good results.
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A very good doublet at a slowish (for imaging) focal ratio will produce good results. However, a very good triplet will yield photographically better result at the same focal ratio.
Blue end of the spectrum usually suffers in a doublet. Attached is a neat chart from Takahashi comparing chromatic correction of a triplet and a doublet both with the same aperture and focal ratios.
@Greg - unless there are reasons not to go with CFF, I think their limited edition 135mm f/6.7 triplet with 3.5FTF might be just the right scope for both visual and imaging (it has a large dedicated corrector resulting in a 55mm corrected imaging circle).