(BllFs6) wrote in message ...

You ASKED about possible accuracy....my answer being that 1/20th wave refractor
wavefronts ARE ALOT easier to obtain than 1/20 wave reflecting wavefronts....

Blll

You forgot some things:

1. Refracting systems has such a factor as internal inhomogeneity,
which hurts wave front too and typically more than for 1/20 wave.

2. For highest wave front accuracy one should use highest rate glasses.
They are expensive regardless of country they were melted.

3. Refracting systems contains sveral surfaces - in any case 2x more,
then reflecting systems.

4. Reflecting systems can be made of zero-expansion substrate - this helps
a lot in manufacturing and testing - and such in reaching necessary
precision. in the same time glasses for objectives has rather large TEC
and very often _different_ TEC.


So, your statement is at least very questionable. But BO's statement about
their objectives quality on 1/20 wave level even more questionable.
We even don't know what the test method(s) was (were) used to prove such
precision.

V.D.