[vsnet-chat 2209] Re: [vsnet-alert 3325]

[bas@lowell.Lowell.Edu (Brian Skiff)]

     Well, it's really an astronomer and Kodak conspiracy.  When they
started the southern surveys with the ESO and UK Schmidts, they decided
to each take a color to speed things up (in principle).  Presumably the
UK Schmidt folks took the J emulsion (blue) plates since the exposures are
shorter than for the red ones, and the weather is distinctly cloudier in
Coonabarbran than in Chile.  Obviously there was no way to insist that the
plates be taken on the same night.
     Compounding this was the fact that the Kodak IIIa plates used for the
southern surveys are "slower" than the 103a emulsions used for the POSS-I
and for the ESO "Quick Blue" survey.  Whereas the POSS-I exposures were
typically about 8-10 minutes for the blue plate and 40-50 minutes for the
red plate, the blue plates in the south are typically 50 minutes, and the
red plates more like 90 minutes.  Similar exposures are being used for
POSS-II in the north (the J survey is in fact finished, and the F [red]
survey lacking only some winter fields).  The IV-N plates for the POSS-II
near-IR survey (far red, or whatever you wish to call it) are like three hour
exposures, so they can't more than a couple of these in a night.  It is
possible that this survey will not be completed since so many of the plates
come out unsatisfactory.
     The IIIa-J and IIIa-F surveys both north and south are substantially
better than the POSS-I, but at the cost of much longer exposures, loss of
having them taken back-to-back on the same night, and a much longer period
necessary simply to finish it.  Ad astra per aspera.

\Brian

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