Re: A question of viewing

On Wed, 23 Apr 2008 23:51:37 GMT, "Mark F." <res049nn@xxxxxxx> wrote:

So I was looking through my new (used) 10 inch dobs last night.
Saturn looked great I could even see a band. (or maybe it was the Cassini
space craft--- Grin)
I also look at Sirius and it looked -- well --umm--- grainy.
Was this the viewing last night in Long Beach, Ca.
Or do I have work to do on the scope?

It will be rare for Sirius to look like a steady point. First of all,
being a point source, its light reaches you through an extremely narrow
column of air, so all sorts of seeing effects cause disruptions. This is
different from planets, which subtend a finite angle. The effect is
moderated somewhat by the large aperture of the telescope (which is why
you don't usually see stars twinkle telescopically), but it's still
there. Second, a bright point source highlights every optical aberration
in your system. Are you saying Sirius looked different last night than
it usually does?
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.