Re: ATM 11.5" mystery glass

["PETER JOHN SMITH" <pjifl@bigpond.com>]

 Doug Miller wrote :

> I agree with Peter about this making a really nice Maksutov. Just for
fun, I cranked
> out a design.  It is a 280 mm f/15.  The design was optimized from 390 to
700 nm
> over a 50 mm full FOV.  All dimensions are in millimeters
> 
> radius           thickness          glass       semi-aperture
> -428.672          20.0000      SK4      140.0
> -441.264        833.7166      air          140.0
> -2124.6229   -808.7166      mirror    150.0
> -723.6668     1088.7166     mirror      42.25
> -685.2910                         image      25.0

My (very hastily conceived) ideas for a MAK using the BaF4 took a slightly
different tack. Involved an extra small F2 lens and were more pretentious.
BaF4 is not really optimum for a MAK shell but in the interests of glass
rescue can be made to perform very well.  Far better performance than from
a refractor.

So here is another possibe approach. It has been calculated for a total
field of 1 deg (tot field of 68 mm)


GENERAL LENS DATA:
 

Eff. Focal Len. :        3899.623 (in air)
Image Space F/# :        13.44517
Parax. Ima. Hgt.:        34.02693
Maximum Field   :             0.5

 
SURFACE DATA SUMMARY:
 
       Radius    Thickness     Glass     Diameter        

     -385.9432        18           BAF4        290.4952     
     -397.2306     758.0182                     295.7344             
     -1905.994    -738.0182   MIRROR      312.9353   
     -610.3182     783.7057   MIRROR        86.94208  
      176.4878       12              F2             70.6396    
      161.252       153.9358                       68.60831 
 IM -503.4361                                         67.9739  

This has a Strehl of well over 0.9 over the entire field.  A real APO
blaster.
BUT at the expense of slightly more complication - the addition of the F2
element.

Now that piece of junk BaF4 looks more attractive.

All the best.
Peter Smith.