Re: C9.25 to a C11
> Assuming the same optical performance the C11 shouldEr. Area og 11" primary = pi* (5.5^2) = 95 square inches. Area of 9.25"
> gather 2.419354838709% more light, but still not get
> you to magnitude 15. What's the additonal cost and
> weight penalty to get those additional photons?
> Geo. Cushing, Delanson, NY, US
primary = 67 square inches. Increase is over 41% (actually very slightly
more, since the secondary on the 9.25, is a little larger in proportion,
than the one on the 11" scope). The 'plus' of the 9.25, is that it has a
flatter field. However to get this, it is heavier for it's size (and
longer), than a 'normal' SCT. The 11", only weighs about 7lbs more than the
Remember 'magnitudes', use a logarithmic scale. It takes a change in light
gathering power, of 251%, to gain one magnitude. So the change in limiting
magnitude quoted for the scopes (0.3 mag), is a much larger change than it
- Actually what is important is whichever is bigger, the CO or the hole
in the primary. The celestron line of scts is not consistent on
this point. I actually have the data in a spreadsheet and have been
meaning to post it to the files section.
I'll try to get to that.
regards Greg N
--- In email@example.com, "David" <Ginahoy@a...> wrote:
> Although this isn't necessarily the size of the hole
> in the primary (which is really what's important for
> your question), the difference is small and the
> proportions similar.
> David Butler