Quote:
Originally Posted by rally
The sooner all scope manufacturers start putting useful numbers (like strehl ratio) behind their advertising the better - as it stands now many buyers are being mislead by the omission of this sort of information.
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The star test is a much more sensitive and easier to carry out comparison between scopes . all the aspects of a superb mirror can't be quantified and contained in one strehl number just by zernicke polynomial point fitting of interferograms. Its not the only basis you would use for for comparing good mirrors from excellent ones as there is so much more involved to a great mirror than trying to fit a polynomial to represent the overall shape using a mathematical approximation.
You only have to compare the synthetic fringe output which is a reconstruction of the interferometer fringers from the polynomial modelling data. Fringe point fitting analysis is lousy at quantifying turned edges and surface roughness, but good at measuring basic spherical aberration.