Re: ATM Laser Beam Test Spherical Aberration

[Bratislav Curcic <epabcc@epa.ericsson.se>]

Steve Bell wrote 

> I've done some calculations with using a lens that changes the f
> ratio down by a factor of 2, and the results look pretty good. Using the
> 12" f/6 (f/3 with the lens) example, the spherical aberration at the 6"
> zone is 0.125" (3.2mm)

As far as I know, reducing the final f-ratio at the testing point REDUCES
the sensitivity of the test (main problem with Ross null test, for example).
The resulting longitudinal aberration ought be HALVED, not doubled.
Check your math again.

Bratislav