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


So here I am, waiting in line for one the Burgess Optical 102mm F6 scopes. Now
I am not expecting anything more than a decent achromat with a decent focuser
and finished a bit better than a Synta scope for my $200.

But there is talk of magic on that forum where Valery snagged that post. It
makes me uneasy, I don't want magic, just a decent scope.

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