Re: ATM Schwarzschild part 2

[Aplanatic@aol.com]

OSLO LT will analyze the effect of a central obstruction on the diffracted spot characteristic.  I have taken James' Schwarzchild camera design and added a central obstruction to it.  The following plot is the encircled energy without the central obstruction:

http://members.aol.com/aplanatic/vesta.JPG

and here's the same plot with the central obstruction:

http://members.aol.com/aplanatic/vesta_co.JPG

As you can see, the 50% central obstruction causes a small fraction of the light to be diffracted outside of the pixel dimension, with a small loss of contrast out to several pixels.  OSLO LT will also plot the diffracted PSF (point spread function) and MTF (modulation transfer function) of the optical system including the effect of the central obstruction. 

The obstruction is added by clicking on the button in the Aperture Radius column and selecting Special Aperture Data.  In this panel, select "Obstruction" and then enter the end-points of the major and minor axes of the elliptical obstruction.

Dave Rowe