OLSO model :
- The model for the "classic" C8 is from Ken Hutchisson and Thierry Berthe, and is a "best guess" given actual measurements and data available.
Optimized design :
- In a Schmidt telescope, the distance between the plate and the mirror is equal to the radius of curvature of the mirror. The distance between the focus and the mirror is equal to half the radius of curvature of the mirror.
- The field correction of a Schmidt-Cassegrain telescope can be improved by increasing the distance between the Schmidt plate and the primary mirror. All other optical characteristics are left unchanged.
Nominal design of the C8 "classic":
Version with the Schmidt plate positioned 230 mm ahead from nominal position :
This version appears to be the optimal one in terms of diffraction limited field.
Radius of the diffraction limited flat field :
The radius of the diffraction limited flat field increases by a factor of four (compared to the classic C8 design) when the Schmidt plate is positionned 230 mm ahead from nominal position.
NB : the focus is optimised to minimized the OPD at the center of the field.
Spot diagrams of the "classic" C8 design over a 0.055° arcmin field (green light and flat field):
Spot diagram of with the Schmidt plate positionned 230 mm ahead of nominal position (green light and flat field) :
