Re: [TASS] photometric vs. non-photometric

[Stupendous Man <richmond@A188-L009.RIT.EDU>]

  Chris writes:

> Before the first Mk III data is imported, we "seed" the catalog with
> Arne's "tassm16" data.  That is we creat a TASS catalog with a few
> million stars in it all with "number of observations" set to zero.
> The tassm16 list is a subset of the FAAST catalog which has good
> astrometry.  As I remember, we use the FASST astrometry until
> the "number of observations" reaches some threshold then we
> compute and use a mean.  The idea was to mimimize the "wandering"

  I have verified that we _do_ use the USNO-A 2.0 catalog subset
provided by Arne -- which is called "tassm16" for short -- to seed
the catalog before we begin importing stars.

  Unfortunately, I have also verified that the threshold in number
of observations required before we use a floating mean position is ...
just one.  Ooops.  So, when a star is observed for the SECOND time,
its position begins to "wander".

  Too late for the Mark III database here at RIT, but definitely
something to keep in mind for the Mark IV, or for other versions
of the Mark III database.

                                            Michael Richmond