After acquiring a large dish it was realized that the dish feed would require careful consideration to get the best out of the system. Two advantages of the Cassegrain system are
1. The "over illumination" of the subreflector is towards the cool sky rather than the warm ground - thus minimising noise.
2. The use of the subflector makes the dish focal length appear to be greater than it is.
A Microsoft Excel spreadsheet was written to enable some what-if's to be tried.
NB this has been updated 2002 Aug 04
DOWNLOAD Spreadsheet as zip file
Last updated 2002 August 04