Re: [TASS] photometric vs. non-photometric

[Herbert R Johnson <hjohnson@PLUTO.NJCC.COM>]

On         Thu, 2 Sep 1999 23:29:44 +0100, Peter Mount <peter@retep.org.uk> wrote:
*>On Thu, 02 Sep 1999, Tom Droege wrote:
*>> There is a scheme to detect sky conditions.  I have allowed a channel for
*>> this and possibly can include it later.  One takes a thermal electric
*>> cooler and glues it between two plates.  One side is allowed to look at the
*>> ground, or anything of constant temperature.  One could water cool one
*>> side.  The other side looks at the sky.  One can use optics, or just a
*>> plate exposed to the sky.  Sky without clouds looks "colder".  So one uses
*>> the TEC to measure a wide area of the sky for its ability to absorb radiation.
*>
*>I have here a collection of old BAA Journals (some older than I am), and
*>there's 3 or 4 different clear sky detectors. Most of them are based on two
*>thermistors (remember it's a 60's design), 1 metre apart, with the lower one
*>just above the ground. When the temperature gradient between them exceeds a
*>certain amount, it indicates a clear sky.
*>
*>Peter

If anyone wants to develop these ideas further - I have too many projects
already - how about posting some of these ideas into a section of the
TASS Web page? References to those journal articles and maybe some abstracts;
Tom's idea about using TEC's; Richmond's references. Also, I would encourage
the Mark III camera users to write something about their experiences with
their cameras, and how the sky conditons have affected the quality of their
data. By creating a place on the Web site to accumulate this information,
someone ELSE will have a chance to come up with some possible solutions
that have a good chance of practical success. As TASS is relatively unique
in wholesale observing in less-than-perfect
skies, what we have to say is worth preserving and to use to support some
solutions.

For instance, our actual observations may suggest that even a "cold"
sky may still be too turbulent for acceptable observations (clear does
not mean steady, ask any amateur astronomer). The accumulated Mark III
datasets offer an interesting opportunity for some QUANTATIVE considerations.
I myself don't think this will be "solved" in an email exchange: it will
take some homework.

Herb Johnson

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