[vsnet-chart 382] Charts and sequences

["Sebastian Otero" <varsao@fullzero.com.ar>]

> > 3- Observers using different sequences and charts- This is one area
where
> > vast improvements could be made if all the VS organizations got together
and
> > agreed on the sequences used for observing stars. Steps are already
being
> > taken in this direction. Through a cooperative effort we have documented
all
> > the charts and sequences for program stars common to the AAVSO, BAAVSS
and
> > RASNZ. In some cases there are widely divergent magnitudes assigned to
the
> > same comp stars. Work has begun on revising these sequences.
>
>     I have a strong concern about the progress of this, since VSNET was
the
> one of the earliest organizations (as early as in 1995 using CCD V band
> photometry, in 1997 using Hipparcos/Tycho magnitudes) which undertook
> the homogenizing efforts of comparison stars using the modern standard
> photometric scales.

>     I wish to think that we are witnessing an intermediate step toward
> a revision (even five years after the release of Hipparcos/Tycho
> catalogs...), but I am simply wondering whether the AAVSO has an intention
> to revise the charts of such well-known variables using modern photometry.


A year ago I started a chart revision specially for southern variables.
That means to update charts and to create new ones.
Since this revision is intended mainly to bright stars -at least at the
beginning- there are very known stars that now have much better charts.
The key of this process is to use PEP(V) or CCD(V) sequences whenever
available or Hipparcos and Tycho/Tycho 2 data.for other stars.
The new sequences are made based mainly on PEP(V) values extracted from the
GCPD and these magnitudes have been available for a long while. No much
interest in upgrading all these awful sequences that most observers keep
using has been demonstrated.
For those of us who want to report accurate estimates there was no other
choice that researching and creating new resources.
New sequences may be available right now because the data are there waiting
(I mean, for bright stars at least).

Enzo De Bernardini (BED) has joined me in this work Although this is most
for southern variables, Pavol Dubovsky has kindly prepared PEP(V) charts for
the norhern hemisphere and let me have them in my webpage too.
You can get a list and the charts at:
http://ar.geocities.com/varsao/Cartas_de_Variables./htm

These charts include the B-V color index between brackets since this is an
important tool to get accuracy now that we are working on the standard
system.

My opinion is that nowadays we have the resources. Star magnitudes are well
recorded up to 10 or 11th magnitude so the only thing that depends on charts
in variable star observing is that "I fell in love with my chart" problem
mentioned by Taichi Kato...;-))
It doesn't depend on who creates the chart anymore. It depends on using
PEP(V) magnitudes and they are available.
What else??

Regards,
Sebastian.



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