From: "Kristopher Barrett" 
To: 
Reply-To: "Kristopher Barrett" 


> Here is the problem though. Commercial telescopes of the cassegrain
> veriety often have central obstructions approaching 37% by diameter
> which Texereau may well have baulked at the idea of. There is however no
> question about these telescopes' ability to resolve very fine detail on
> the planets. They are in fact among the top performers. So my question
> is (in the words of a true potiticain) who is almost right and who is
> almost wrong?

These commercial OTAs are Schmidt-Cass., and have a corrector plate, rAther
than a simple window. They fix contrast problems caused by the big
secondary via a bigger focal length. And yes, they are a compromise.

You can improve contrast by making the secondary smaller and still keep the
long f-stop....Meade sells some Schmidt-Newtonians that do just that.

You could also just use a greater perscription for your corrector plate:
http://members.cox.net/rmscott/lh_scope/

--
Regards,
Kristopher Barrett    http://www.cotse.net/users/kbarrett

--- BBBS/NT v4.00 MP