Re: ATM Folded Newt Question

["Bob May" <bobmay@nethere.com>]

The "column of air" is relating to the diameter of the light beam that is
coming down through the atmosphere.  What happens is that the larger the
diameter, the more the slope of the refraction error is seen.  Thus a 6"
scope will be seeing a 1/4 wave change of the wavefront while the 12" scope
will be seeing a 1/2 wave change in the wavefront at the same time, more or
less.  Seeing that the changes move the apparent source of the light by some
amount, you get the fuzzyness of the image to be larger in the larger scope
and it gets worse because the larger scope is also able to see to a better
resolution so the image is further from a well focused sharp image than the
smaller scope would be.
Hope this concept of the problem is clear now.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net