[Aavso-photometry] BRI Comp Star Value when reporting OBS is the Chart V value?

[arne]

Tim Crawford wrote:

 > Arne,
 >
 > Are you saying that if we have a chart with a V
 > magnitude of say 10.0 that when we also REPORT BRI OBS
 > that we use 10.0 in the comp star field, provided that
 > BRI sequence data is available?
 >
 > IF SO, me and a lot of other folks have been doing it
 > differently for a number of years.... makes me wonder
 > about how data will be looked at in the future if we
 > change horses in mid stream, so to speak.
 >
 > In addition, some of us report the three decimals, if
 > available for comp values as that is how we measured
 > the photometry..... I would then suspect this might be
 > contrary to the New Policy, if such is in fact true,
 > of reporting just the V value from the Charts, which
 > usually only have one decimal.
 >
 > This of course then raises the question of did the
 > observer use the three decimal sequence value or did
 > the observer use the rounded up Chart value when doing
 > the photometry?
 > If we are only to report the Chart Value in ALL cases
 > when other color data is available (i.e., BRI) and
 > even though we have un-rounded up sequence data with
 > more decimals that we used for the photomety... then I
 > would hope you could get a special alert or something
 > out to this effect so that the word gets around.
 > Thanks for the clarification, Boss... and if I read
 > your reply to Keith in error then I hope you and other
 > readers will chalk this email up to another senior
 > moment of the sender.
 >
 > Also, I would hope that what ever changes are made or
 > suggestions as to how we respond in different
 > situations that the need to have to figure out a comp
 > code (not enough of 'em to deal with CCD issues) and
 > then enter a comment be kept TO A MINIMUM.
 >
 > Tim Crawford CTX
 > Arch Cape Observatory
 >
 >
 > --- arne <arne at aavso.org> wrote:
 >
 >
 >> Enter the chart mag - that is the label that we use
 >> to ensure we know
 >> which comp star you were using.  We know what its
 >> BVRI magnitudes
 >> are from the calibration.  The exception to this is
 >> if there is
 >> no filter information for a given comp star.  Then
 >> give its label
 >> in the compstar field, but place in the comments
 >> what magnitude you
 >> assumed for that star.

---------------------------
OK, here is the way to handle comparison star entry.

In WebObs, the data entry indicates:
"Comparison Star(s) If more than one, separate with commas"
You should enter here the *labels* of the comparison stars
from the chart (like 102 or 154).  That provides us with the
necessary information to identify the star.  This holds true
whether the submitted observation is B,V,Rc, or Ic.

Since currently the chart ID is just the calendar date on which
the chart was made and does *not* usually indicate anything about the
creation date of the photometric sequence, we then additionally
need the standard magnitude you used for your comp stars.  Provide
those in the "comments explained" section, and give an "O" code
in the comment codes field.  In the Comments Explained field,
use the B,V,Rc,Ic magnitude of the comparison star(s) appropriate
for the bandpass of the submitted observation.  The exception
to this is if the chart is a CCD or PEP chart that has
the standard magnitudes printed in a table on the chart, then just
supplying the chart ID and the comparison star labels is sufficient.

Note that the purpose of the "comparison star" field in WebObs for
CCD observers is for HQ and researchers to identify which comp stars
you used.  So Tim's previous method works in most cases and you
don't have to send in corrections or anything.  However,
for future submissions, try to use the method described above.
Arne