One can also stop down the aperture on the SCT during mediocre seeing
by making a mask with a circular hole on one side of the secondary
obstruction and placing it just in front of the corrector plate. This
is a common procedure, so I have read. This is also useful for making
estimates of brighter variable stars since it is known that estimates
are more reliable when the star is, as I recall, within 2 to 4
magnitudes of the magnitude limit for your scope.


>
> Aperture rules 95% of the time in astronomy. However, aperture does
not rule
> necessarily when VISUALLY observing bright objects like the moon and
planets.
> Unless you are blessed with sub-arcsecond seeing, a high contrast,
optically
> superior scope can offer better views of the planets than a larger
scope under
> the same seeing.
>
> With all that said, I'll second Bill's advice to keep the 12". The
7" Mak
> doesn't buy you much in terms of contrast over your 12". If you
where buying a
> scope from scratch, and all you wanted to do was observe the Moon
and Planets,
> I'd say get the 7" Mak or a high quality refractor. But you already
have a
> fine all around scope.

==
J Nordby

Interesting web sites:
http://www.powerbasic.com
http://www.perl.com/perl/
http://www.linuxworldexpo.com
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