[AZ-Observing] Re: Observing Weather this Weekend
- From: "cvsc1" <cvsc1@xxxxxxxxxxxx>
- To: <az-observing@xxxxxxxxxxxxx>
- Date: Tue, 31 May 2005 21:59:15 -0500
Brian,
Out of focus I can get about 10 rings on either side of focus and can reduce it
to 2 rings. See this link for the example I followed.
http://voltaire.csun.edu/tmb/tmb4.html
Also had Steve Dodder spend a few hours with it and he liked what he saw. He
taught me a lot about what to look for that night.
Stan Clark
webmaster
saguaroastro.org
---------- Original Message ----------------------------------
From: Brian Skiff <Brian.Skiff@xxxxxxxxxx>
Reply-To: az-observing@xxxxxxxxxxxxx
Date: Tue, 31 May 2005 19:48:57 -0700 (MST)
>>> ...how many rings can you see on a star test? I consistently lose
>>> count at around 10.
>
> Is this, like, in focus?! The spherical aberration must have to be
>terrible to see so many diffraction rings if that much of the light is
>not in the Airy disc (where it's supposed to be). Am I missing something,
>or is ring-count actually used as an optical test? In an ideal optical
>system, the third ring has only a small fraction of a percent of the total
>light (i.e. many stellar magnitudes fainter than the central disc)
>so shouldn't be visible at all. Tenth ring?
>
> More generally, the Stans seem to be describing a mix of physiological
>and real optical effects, so it's not super-obvious what's going on in
>Stan G's original query.
>
>\Brian
>--
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