"Jon Isaacs" wrote in message
...
I wonder if those values are determined with an interferometer or other
test
method(s)?

In general, I think the properly conducted interferometer test results
would
show lower values, but a bit more realistic values.

Dan McShane

Now, 1/20th lambda implies a surface precision at a single frequency. But
given that the objective in question is an achromart and about 127mm at
about
F8, I wonder how much difference such precision would make since the
design of
such an objective is quite a compromise????

In other words, ignoring the issue as to whether these really are 1/20th
lambda, is there anything to be gained by making an 127mm F8 achromart to
1/20
th Lambda???


Jon,

I had that thought too, as a post script.

Does 1/20 wave really buy you anything with an f8 127mm where the system may
be swamped (comparatively speaking) by chromatic abberation?
Still, at $200 even if it`s really *only* 1/8-1/10 PTV, (and has RMS in
line with those values) it seems like a hell of a good deal. As long as the
CA is tolerable.

Dan McShane



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