Re: Re[4]: [ATM] Chromatic effects visibility

["vladimir sacek" <vlad@copper.net>]

Hi Richard,

> Wynne made reference to four ways of correcting an RC in :
>
> Wynne, C.G., 1980. Mon.Not.R.astr.Soc V193, pp7-13
> "Field correction of a Ritchey-Chrétien telescope at several
> focal ratios."
....
> (3) The addition of a doublet lens between secondary mirror and
> focus.
> (4) As (3), together with a change of secondary mirror
> asphericity

I should have said "textbooks" instead of "literature" (which I have very 
limited insight into).
Single aspheric plate is less than perfect field corrector,
and likely more difficult to make than a pair of simple lenses.  It may be 
that a doublet corrector requires designing of an integrated system for 
really good performance, although better a word for the one you came up with 
is "excellent".

One think that is unclear to me is why the system is only
"diffraction limited" between (from the memory) 300nm and 1200nm, if the 
"worst case" blur size is only a small fraction of the Airy disc.

Vlad 


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