Ron Wodaski o Mewlonie 210 napisał : "Over the last year, I've used an 8" and a 9.25" SCT, a 6" Mak-Newt, a 6"
Mak-Cass, a 4" fluorite refractor, an 8" Cassegrain, and some other scopes
over the last both visually and for CCD photography.
I found that the SCTs have, in general, somewhat weaker contrast than other
designs. I also found, as someone else mentioned, that they have a very wide
spread in image quality, so if you go that way be careful and look first!
The Mak-Cass also had less contrast than other designs I've looked through.
The obstruction size was similar to the SCTs, so perhaps that is the
culprit.
The 6" Mak-Newt had better contrast than the SCTs and the Mak-Cass. That
particular scope had pinched optics which I did not get around to fixing,
but was still very high in contrast. It was comparable to the 4" fluorite
refractor in contrast at most powers, and superior to it at higher powers
(200x to 275x).
The 8" Cassegrain had superb contrast, best of any scope I've owned, but it
was a very high quality scope (it was a Takahashi Mewlon 210). I can't say
if the Cassegrain design itself is higher in contrast, since the scope
manufacturing was so good. This scope had better color saturation than any
other scope I've owned.
The best scopes I've seen on contrast were at opposite ends of the refractor
size spectrum. My little 60mm fluorite (Takahashi FC-60) is absolutely
amazing in contrast, but it only handles powers up to around 150x before
contrast starts to drop. It's still sharp at 200x, but contrast is less.
The other is also a Takahashi, an FCT150 that a friend owns. Even at 600x,
it has remarkably good contrast. However, it is no longer in production and
goes for absolute premium prices.
If I were to make a recommendation, I would go with the Mak-Newt for
contrast. They are also pretty sharp, and the combination of sharpness and
contrast is, to me, the ideal. For example, although the Mewlon has superb
contrast, the 9.25" SCT I have is just as good on detail -- it just doesn't
have the rich color on planets that the Mewlon does."
Ron
Jeszcze zdięcie Giorgio Mengoli z Włoch
http://digilander.libero.it/gm2/Mos6.jpg