[Aavso-photometry] u crt sequence suspects!

[arne]

Yenal Ogmen wrote:
> Hi all,
> 
> As you may know, one of U Crt sequence stars, "127
> Comp S" is in the suspect list. A few hours ago, when
> I tried to do photometry of U Crt with comp star 130
> (GSC 4928:41) I got approx. 1 mag brighter result than
> the expected value, observed from other observers' obs
> at around the same time. Therefore I used 114 to get
> reasonable estimate. Anyone know anything about this
> star (GSC 4928:41)? It is neither in the suspect list
> nor in VSX.
> 
I've observed these stars multiple times in the process
of calibrating this field from Sonoita Research Observatory.
None of them are variable to the best of my knowledge.
However, the chart photometry is far in error.  This is
one of the fields that will change with the upcoming
compDB/VSD update.  You can see this by clicking on
the "Comparison Stars" link, where there are lots of
comparison stars shown in the table, but with no
accompanying photometry other than their label.
Remember, the October 2007 update was only for those
stars that did not change by more than 0.2mag from
their labels - so you can be sure that most of the
U Crt stars are going to change dramatically!
The old photometry came from a preliminary chart from
1977, with a photometric sequence from WML and LEH.
The new photometry for the three stars that Yenal
mentions are:

label  V      Verr
114  11.358  0.012
127  14.274  0.012
130  14.038  0.016

This kind of error is exactly why we are updating the
photometry, and why everyone has to pay attention when
the update happens.
Arne