Mirror specifications

Primary

Secondary

Telescope

               in       out      ccd focus
Focus        1399.4    2796.6      2048
Analog       1301      2998        2103

B = Back Focus           = 15.68
D = Dist Between Mirrors = 47.63
F = Effective focal len  = 72.00

C1 =  Primary Schwarzschild deformation coefficient

C2 =  Secondary Schwarzschild deformation coefficient


       ( B - F )            15.68 - 72               -56.32
C1 =  -------------  =  ------------------   =     -----------   =  -0.008211
       2 * D * F          2 * 47.63 * 72             6858.72



       ( B + D - F )      15.68 + 47.63 - 72           -8.69
C2 =  --------------- = ----------------------  =  ------------- =  -0.005818
         2 * D * B         2 * 47.63 - 15.68         1493.6768
 

Note:  The values may not be correct because Wikipedia defines backfocus from 
secondary to focal plane, and DFM appears to define backfocus from the 
primary to the focal plane.  If that is correct, B would be 15.68 + 47.63.



B = Back Focus           = 63.10
D = Dist Between Mirrors = 47.63
F = Effective focal len  = 72.00


       ( B - F )            63.10 - 72                -8.90
C1 =  -------------  =  ------------------   =     -----------   =  -0.001298
       2 * D * F          2 * 47.63 * 72             6858.72



       ( B + D - F )      63.10 + 47.63 - 72           38.73
C2 =  --------------- = ----------------------  =  ------------- =   0.006443
         2 * D * B         2 * 47.63 * 63.10          6010.91
 

At least the second case has different signs for C1 and C2, which is expected because
the primary is concave and the secondary is convex.