Re: ATM 310mm F/1.55 Schmidt camera update

[Jan Bentz <jbentz@inreach.com>]

Dominic.Luc-Webb@molmed.ki.se wrote:

> I have now posted my OsloLT file and some tricolor spot diagrams for the 310mm
> F/1.55 Schmidt camera. I will 
> post some Ronchgrams in coming days. I welcome any 
> remarks about further improving this design....
> 
> http://www.megspace.com/science/stp/catadiotric/catadiotric.html
> 


Dominic -- I think there may be something wrong with the way you are 
deriving or using the coefficients for the correcting plate.  The spots 
looked too large to me with the neutral zone at 87% radius and should 
not have gotten smaller with the neutral zone at 50%.  I don't use Oslo 
  so I did  a cursory run through of your system with another ray tracer 
and got a spot size on axis and at 2 deg off axis C-F light of about 
.005mm with the neutral zone at 87% where spherochromatism is a minimum. 
  Spherical correction can be gotten with the neutral zone at any 
position so will look good autocollimated.  Satisfy yourself of this 
before you start grinding.  At this speed (f/1.55) spherochromatism can 
be quite serious.

The coefficients I got were A2 = -.000571844, A4 =.0000162898, A6 = 
.00000003

Jan Bentz