[AstralTraveller (David)]

Hi,

I'm toying with ideas for backyard observatory and scope. There are a few things I might want to do with the scope (imaging isn't one of them). For the present discussion lets assume the scope will only be used for visual viewing of the moon, planets and sun. Let's also ignore issues of convenience, ergonomics and price - I am aware of them and will factor them into my considerations. I'm only asking about relative optical performance of these two options.

1) I have a full thickness 10" f/8.2 newtonian mirror (with 2" secondary) which I believe to be at least reasonable quality. It was made for me by Astro Optics in 1975. For years it was in a poorly made scope with terrible thermal management but it worked well enough often enough for me to think the optics must be good. It could be built into a dobs - this time with a good thermal management, baffling and a motorfocus. I could also consider downsizing the secondary to 45mm.

2) I have a Vixen Sphinx head and this should be able to support a Celestron C11. (The mount is rated to 23kg, the tube is 11kg and it will be out of the wind.) Theory says that the larger central obstruction of the SC will reduce contrast more than in the newt but, on the other hand, it is 1" bigger and detail is easier to see if the object is brighter.

So, would the slight increase in aperture outweigh the greater obstruction? Which one would you sooner walk up to and look at Saturn? Thanks for your experience or conjectures.