Re: cassagrain doublets

Narasimham wrote:
Dave Schaack wrote:
"Narasimham" <mathma18@xxxxxxxxxxx> wrote in message
news:1151744499.013480.317660@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
For a spherical primary I obtained
an undulating Schmidt corrector type reflector, so was curious to know
when aberrations (spherical etc. ) are not allowed what they all are
and how difficult it is to make them, as they are not spherical any
more. TIA


You are certainly asking the right question. The Ritchey-Chretien is the
aplanatic one, that is, it is corrected for both spherical aberration and
coma. It is also very difficult to make, so is primarily seen only in
professional astronomical observatories. Some of the others were developed
specifically because they are relatively easy to make; each has some
advantage.

I suppose The Ritchey-Chretien is a central segment of a one-***
hyperboloid. When ANY conic section can be used, does it include the
two-*** hyperboloid as well? (designed with beam reflections like
Coude?) .. suggestion as the two *** hyperboloid is easier to make,
easier than the spherical mirrors, by straight motion of a grinding
wheel skewed to the (would be) axis of telescope.

Regards
Narasimham

My query was in obvious error, .. that should have been:

I suppose The Ritchey-Chretien is a central segment of (concave half of) a two-***
hyperboloid. When ANY conic section can be used, does it include the
one-*** hyperboloid as well? (designed with beam reflections like
Coude?) .. suggestion as the one *** hyperboloid is easier to make,
easier than the spherical mirrors, by straight motion of a grinding
wheel skewed to the (would be) axis of telescope..

Thought of RF microwaves in extension ! The answers are in
place,Thanks again.

.