Re: [TASS] photometric vs. non-photometric

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

On         Fri, 3 Sep 1999 16:22:27 -0700, Chris Albertson <calbertson@LOGICON.COM> wrote:
*>Andrew Bennett wrote:
*>
*>> ... Otherwise one knows nothing about
*>> what somebody decided to throw away. A lot of the gaps in
*>> tenxcat are like this: was a star below some limiting
*>> magnitude (oops - I mean above; you optical types measure
*>> backwards) or was it not measured. It makes a big difference
*>> to the statistics.
*>

Andrew requested more info on the criteria for rejecting TASS Mark III
images for data analysis. I'd be glad to add or reference that information
by site (each site decides what data to process) to my recent Mark III
Tech Note, if it is provided to me. There has been some discussion of
this which would be in the TASS email archives. A review of the TEch
Notes would be incrementally helpful, again my TEch Note does (or will)
reference those notes, I lost some edits of my TN.

*>It is always hard to answer the question "why is something NOT
*>here?".  For the tenxcat list it helps to know that it is intended
*>to be a subset of the "real" TASS catalog.  It contains only the
*>stars that by Michael's criteria have "good data".  There is another
*>table in the database the "tass catalog" that contains _all_ stars
*>seen by TASS.  So if the star is not in tenxcat but IS in the
*>tass_catalog it is due to a decision by the author of tenxcat.

...and the TenXcat Tech Note does an excellent job of describing the
criteria for inclusion. Andrew apparently requests similar information for the
data in the TASS Mark III database as accumulated by Richmond. He,
and perhaps others, would be interested in the DETAILS, not in general
statements, about criteria for NOT processing Mark III image data
into starlists and eventually into one database or another. These would
be determinations by the participants: raw data would not be helpful
unless it was accompanied by explanations as to WHY that data was or was
not included.

Such explanations might also be informative to people interested in the
disucussion of detecting "good skies".

Incidently, Chris, I am careful to describe what you call the "real
TASS catalog" in the way I describe it above. Other TASS members have
their own databases of their observations: Glenn Gombert's own database
of observations is real enough for instance. I call the results of TenXcat
a CATALOG because Richmond has all but published it as a list of
real stars that he stakes his reputation on as being ready-to-verify or
observe. It is a catalog in the ASTRONOMICAL sense that you can in principle
pull it off a shelf and take it to your telescope, with some confidence
based on your review of the stated criteria of inclusion. I understand it also
happens to be a table in a database, but most of the end user's of TenXcat
(such as Bennett most likely) will not know that.

Likewise, "the real TASS database" is certainly a DATABASE. If the
database "system" also has tables called catalogs, I myself would not call
them ASTRONOMICAL catalogs unless they were as well-qualified as Richmond's
TenXcat catalog. Chris and I have argued this before, maybe the distinction
of "astronomical catalog" vs. "database catalog table" is helpful. I thought
about arguing this out in detail but I suspect those who would be most
concerned already understand the distinction.

Herb Johnson

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