That is not really an "airy disc" but you do need to see that pattern before you
can see an airy disc. To see an airy disc in a 8" or larger sct try a 2-3" off
axis stop at 100-150x. Once you are familiar with it you can try to see it at
full aperture. It is very small in a large scope and needs high power and sub
arc second seeing to see to actual disk in a large scope.
Bob

Frank & Linda Wheeler wrote:

> Hey David. Been there done that..according to the astronomy dictionary Airy
> disk: the central spot in the DIFFRACTION pattern produced by a point source
> of light by a circular aperture. It is used in comparison of Resolving
> Power. Yeah but what is it? Diffraction: light bending around an obstacle in
> its path will produce a pattern of light and dark lines, in our case the
> secondary mirror is the obstacle. By centering a star in the eye piece and
> then changing the focus, you should see the shadow of the secondary
> surrounded by the "Airy Disk"! The doughnut should be round, the same size
> w/ circular lines in the white disk. It blew me away the first time I
> collimated my scope successfully and saw the bulls eye pattern..Hope this
> helps...Frank W.----- Original Message -----
> Sent: Tuesday, July 03, 2001 5:37 AM
> Subject: [M]: Airy Disc?
>
> > Hi all, I've been collimating my scope for the first time, and keep
> reading "AIRY DISC" could someone please tell me what an Airy Disc looks
> like? I need a visual. I guess I have a lot to learn. Thanks for all your
> help always, Dave
> > __________________________________________________________________
> > Get your own FREE, personal Netscape Webmail account today at
> http://webmail.netscape.com/
> >

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