Re: Note on photometry of DS23

[Tom Droege <tdroege2@earthlink.net>]

Patrick and all,

There are plenty of things that need to be looked at in this data.  Below 
is just one example.  If anyone wants to investigate something like this, 
first have a go at something similar in DS20 if you have it.  If not, or if 
you can't find an example in DS20, then ask for data sets by the 
appropriate .cal file.  I can look these up and then send you an 
appropriate raw data set.

Who knows what causes this.  Clouds are suspect, but my first pass at 
eliminating cloud data also eliminated all the interesting 
data.  Sigh!  You all are certainly encouraged to look at the data and find 
the causes of problems.

Tom Droege

At 11:42 PM 7/1/02 -0700, you wrote:
>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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