[ATM] BK-7

[Richard F.L.R. Snashall]

  On 3/25/2011 9:27 PM, Francis J. O'Reilly wrote:
> I have a great piece of BK7, eight inches plus diameter, an inch thick. I need to do something with it. Maybe a Maksutov corrector?

I agree; the corrector would probably need to be sagged.
But you might also consider a BK7 Sandwich:

Title: trp03-15x
200 mm f/11.66 Triplet

Surf     Radius  Thickness  Glass  Diameter

  STO   Infinity   -4.66032              200
    2   1075.218         10     F2       205
    3        600         25    BK7       205
    4       -600         10   B270       205
    5  -15257.47   2302.492              205
  IMA  -868.0485                          44


The risk here is the available quality of B270, but then,
you did not say whether it was really BK7 or just bk7.