Rob Brown's notes to me ---
Your binoscope project is compelling, especially because you are thinking of using the MPCC. As was noted recently a hyperbolic mirror does better with the MPCC, so I generated a design for you. Obviously you should parabolize the mirror first and see how it performs with the MPCC. If you’re not happy then here’s the solution. Maybe.
The challenge for your design is that there is a high degree of spherochromatism (each color comes to focus but at a different position.) The good news is that the problem goes away with a narrowband filter and possibly looks just fine with a dual band (h-alpha and OIII). Blue is horrible.
The spherochromatism is much improved for F/3.5.
Your new conic is -1.31. Not much change, of course star testing will drive you to perfection. Field curvature is something like 700mm convex as seen from the viewing side, with a sag of 0.198mm. There isn’t much improvement focusing inward, stars out at the edge will be blobs no matter what and they might change shape slightly. But those are low-power blobs!
Dimensions in millimeters. MPCC lens model is from Ed Jones via cloudy nights. *LENS DATA MPCC 8" F/3.1 Hyperbolic SRF RADIUS THICKNESS APERTURE RADIUS GLASS SPE NOTE OBJ -- 1.0000e+20 2.6186e+18 AIR 1 -- 445.000000 113.252735 SX AIR AST -1.2598e+03 -564.333548 V 101.600000 AS REFLECT * 3 -114.264000 -4.009000 25.356054 S N-BK7 C 4 -53.863000 -5.641000 24.695853 S AIR 5 -199.816000 -6.535000 24.623441 S N-BK7 C 6 199.816000 -55.000000 24.293752 S AIR IMS -- -- 16.631964 S * *CONIC AND POLYNOMIAL ASPHERIC DATA SRF CC AD AE AF AG 2 -1.3200e+00 -- -- -- -- *SURFACE TAG DATA 7 DRW ON *PARAXIAL CONSTANTS Effective focal length: -635.089994 Lateral magnification: -6.3509e-18 Numerical aperture: 0.159977 Gaussian image height: 16.630417 Working F-number: 3.125443 Petzval radius: -657.471819 Lagrange invariant: -2.660490
