[Aavso-photometry] YZ And

[arne]

I should have referred to my earlier posting; sorry.  For YZ And,
it will be fairly straightforward to update the comparison star
database with new BVRI photometry, once we fix the bug that prevented
the import of the existing sequence from the 1999 chart.  Once we
include the coordinates of the sequence stars in the database,
then we have automated software that finds those stars in the Sonoita
calibration files and updates the comparison star database.  So the
sequence team does not initially have to get involved in YZ And.

However, for fields where no previous sequence existed, the full steps
mentioned below have to be taken.  Even for YZ And, once the updated
photometry becomes available, it is quite likely that the sequence
will need to be revised, with some stars added and others dropped
depending on their updated photometry (since we try to space the
sequence stars pretty evenly in magnitude). I've gone through the
old sequence for YZ And with the new photometric calibration,
and there are some drastic revisions that will show up, once the bug
is fixed.  For examples, the 118 star is 12.3; the 123 star is 12.9;
the 145 star is 16.0.  Fields where the sequences are poor (like this
one) are often avoided by the observers since they can't get reliable
estimates, and that can be the cause of these fields being in the
"needs more observations" list.
Arne

arne wrote:
> Gordon Myers wrote:
>> SZ And is on the list of targets needing observation published July 1.  The
>> observing chart from VSP does not show any comp stars within about 1.5
>> degrees.  Any chance to identify closer comp stars, or do we need to use all
>> sky photometry techniques?
>>
> We have an observing program at Sonoita Research Observatory (SRO)
> to calibrate every Mira field that is in the AAVSO Validation List.
> YZ And is one of those, and a 4-night BVRI calibration is available.
> There are two steps in using this.  First, someone on the Sequence
> Team needs to look at the calibrated stars and pick out a sequence.
> Then someone needs to load that sequence into VSP/VSD.  Then, whenever
> observers access the field through VSP, they will have comparison stars
> showing and available through the photometry table option.
> 
> When will this happen?  That is the tougher question.  We have a
> Sequence Team that is too small right now, and the few active
> members are involved in updating the existing comparison star
> database in preparation for the next release in a couple of weeks.
> We have about a hundred corrections that observers have made
> through CHET to existing fields that need to be addressed.
> Then, a plan of attack for the new calibrations needs to be in place.
> 
> Right now, SRO is in the Arizona monsoon, and so we have a 2-month
> lull in new photometry.  I'm waiting for some tools to become
> available for the compDB update process.  But I'm expecting some
> large changes in how comparison stars are handled in the near future.
> If you feel ambitious, I've posted the YZ And calibration at:
> ftp://ftp.aavso.org/public/calib/yzand.dat
> There is a README file there that tells you the format of each of
> these calibration files.
> Arne
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