Thank you Mark, that is very interesting. I note that for a fast F5 refractor
it is better to have a mirror diagonal. Is a mirror diagonal erect image ?




Mark De Smet wrote:

I asked this previously, and there were some very helpful answers:

http://groups.google.com/groups?hl=e....com&frame=off


Or, if the above link doesn't work, see he

http://tinyurl.com/pybz

Mark