ATM R-C questions

["Asaf S.-T." <dark_observer@yahoo.com>]

Hi,

My current plan of my Asteroid/Comet-Search system
(which will also be used for Astrometry), is a 16"
Ritchey-Chretien, and on it a 9" Newtonian (Richar
Schwartz kindly sent me the blank. I'll get it in two
more days).

Now, my first idea of the system was two Newtonians,
the same aperture as I said before. That's why I
needed the 9", so I will also have a big field.

Now with R-C, I don't need if I need the 9" to be
connected to the R-C, I mean, the R-C gives me a great
field, great Astrometry work, so is the 9" so
important as it was?

Another question I have is about Mirror quality for
Astrometry. Does the Mirror quality define the quality
of my Astrometric work?

Finnaly- the reason of this e-mail- mounts for
cessegrains. I need the R-C to be a star-tracker, so
can I just make it a Dobsonian with setting circles?
Why is it that every cessgerain is NEVER a dobsonian?

Thanks!
===
Asaf S.-T., Amateur Astronomer & ATMer.
Visit: http://www.maxnm.com/asaf/pages/
__________________________________________________
Do You Yahoo!?
Bid and sell for free at http://auctions.yahoo.com