To: atm{at}shore.net
From: Jim Burrows 
Reply-To: Jim Burrows 


At 07:25 2003-04-12 -0400, sd wrote:

>Using a transverse aberration model, basically straight from Texereau, with a
>few modifications, I arrived at the following expression, which the maximum
>depth of error on a diagonal,
>
>   surface error = .86*lambda*minor axis/diameter of primary

Due to the messy wave (photon, quantum, etc.) nature of light, it doesn't
go where transverse aberration says it does.  Here's a simpler, but truer
requirement for primary and diagonal surfaces:

         sqrt(RMSpı + RMSdı/2) < 20 nm

with RMSp and RMSd the surface RMS of primary and diagonal.  Dividing the
diagonal MS by 2 is for a 45 deg diagonal (I think).

Exercise for the reader:  write down a formula for the requirement in terms
of SRp and SRd, where the SR are the Strehl ratios of the two surfaces. 
Note:  for a cass with straight-on secondary, the system Strehl ratio is
SRp*SRs, so how do we work the 45 deg diagonal in this case?

         -- Jim Burrows
         -- mailto://burrjaw{at}earthlink.net
         -- http://home.earthlink.net/~burrjaw
         -- Seattle N47.4723 W122.3662 (WGS84)

--- BBBS/NT v4.00 MP