Chris L Peterson wrote in message . ..
On 19 Mar 2004 14:52:53 GMT, (BllFs6) wrote:

Sorry, getting to my point here....now I find it hard to imagine if I built a
40 inch scope and it was located somewhere near sea level in the southeast USA,
that I would get anything remotely close to .1 arc second star images on CCD
frames ranging anywhere from 30 seconds to many minute exposures (and lets
assume seeing is our only problem....other problems such as tracking, scope
vibrations, tube currents, overly warm observatory etc etc have been
eliminated)....

Now, my WAG is that such large scopes probably dont exceed .5 arc seconds
imaging give or take the majority of the time...if that good...

I don't believe I've ever seen a deep astroimage with 0.5" resolution. At very
good sites, with good equipment (see, for example, what Adam Block is getting at
Kitt Peak with a 20" RCOS on a Paramount- basically as good a setup as you can
get) 2" is common, rarely pushing down towards 1". That's the best any scope, of
any size, can do through the atmosphere (without using adaptive optics, which
doesn't exist for amateurs except the for the trick of selecting from many
frames).

Also, if you want to do deep sky imaging, you'd be better off retiring to the
southwest than the southeast g.

Heh!

What many (apparently) don't realize is the seeing conditions and arcsecond
resolution at many of the professional observatories aren't as "good" as one
might imagine.

An interesting document that describes site selection and tests (with examples)
can be found he

snap.lbl.gov/pubdocs/Seeing_at_Observatories_v3.0.doc

"LBL" = "Lawrence Berkeley Labs"

A number of other fascinating articles can be found he

http://www.llnl.gov/str/Indexlist.html

such as:

http://www.llnl.gov/str/Olivier.html

concerning laser guide stars for adaptive optics.

"LLNL" = "Lawrence Livermore National Laboratories" (the nuke lab :-)

LLNL was instrumental setting up many observatories with adaptive optics using
technology originally developed for SDI ("Star Wars").