Note on photometry of DS23

[Patrick Wils <patrickwils@yahoo.com>]

Maybe this has already come up before, but looking at
the DS23 data centered around RA=64 degrees, for JD
...312 and 313, one sees a lot more scatter for the
first day then for the second day for a number of
stars.  Standard deviations are three or more times as
large on the first night.  This is clearly visible in
e.g. the objects 946, 950, 1840 and 1954, all with a
substantial WS statistic.  This means that V and I are
more or less correlated.  But the phenomenon can be
seen in objects with WS < 1 as well, e.g. 1944, but
less pronounced, while in others the scatter is the
same on the two nights (e.g. 1912).
I have checked the other field centered on RA=101
degrees, which was imaged on these days, but I didn't
find an example of the phenomenon (I may have
overlooked them).
Does anyone have an explanation for this ?

Patrick



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