Quote:
Originally Posted by KenGee
As you know a F1.5 has a very curved focal plane. The camera was designed to be used with film that was curved to the focal plane via a film holder. CCD are very flat so the only way to do it is to use a field flatener. Now as long as you put the lens very close to the focal plane then very little aberrations are introduced.
A signal panoconcave lens is all that is needed.
Now Telescope Optics by Rutten and van Venrooij tells me the required curvature is calculated by
R= (f(n-1))/n where n is the refractive index of the glass
For a F1.5 system using BK7 glass
R = 300(1.52237 -1) 1.52237 = 102.93
I think 100mm would be good enough, this is a off the shelf item.
I will use a APS size ccd this shouldn't be to taxing for it. I will test and If need be get a custom lens made.
|
That's probably all that happens in those Celestron Faststar assemblies that were being touted as the bee's knees a few years ago.
Will that corrector also correct for coma ? I imagine it would be severe at f1.5
I was aware of 5" and 8" versions , didn't know about (or forgot) the 14" version , I thought they also had an 11" version too.
The 14" version would be a stupendous catch once modded and corrected for flat field coma free CCD imaging .... they'd be rare as hen's teeth too.