[vsnet-chat 5193] Re: [vsnet-chart 385] The future of charts and sequences

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Re: [vsnet-chart 385] The future of charts and sequences

> U Gem is not the only example of a sequence that needs to be looked at and
> revised or improved. There are several hundred stars that have very bad
> AAVSO sequences and charts. AAVSO is well aware of this, and contrary to the
> general consensus, is not reticent to change or improve their charts. I have
> a list from HQ of over 400 stars prioritized for new, improved charts. The
> problems with the existing sequence for U Gem are trivial compared to some
> of the stars on this list.
> 
> Like any organization, AAVSO does not have unlimited resources or manpower
> to attack this problem. For many years nearly all the responsibility of
> chart production for AAVSO has fallen on Charles Scovil. He has done a
> remarkable job, and continues to this day to produce charts that are part of
> an extraordinary legacy in variable star astronomy. He now has some help
> tackling the next generation of charts and sequences.

   Since human resources are always limitied, it would not be the best
solution to rely everything on the AAVSO.  Variable stars are, and will be
being discovered in millions, creating a new set of standard charts is
easily an endless job!  Let's gather human intelligence around the world!

   I think the simple strategy what Sebastian Otero suggested can be the
final solution.  What we need to harmonize is not on the still unseen
fixed set of "final" charts, but on fixing a few standard rule (V mangnitude,
color selection, criterion of exclusion of data with large errors,
treatment of double stars, proper inclusion of all known suspected
variables).  Once such a set of standard rules can be fixed,
we don't need to bother anyone else other than to wait for reliable two color
(e.g. V and B) photometry of the intended targets.  To the required
precision of visual photometry, introduction of such a rule will be
sufficient in most cases: observers only have to report that "they have
followed the V-band sequence (selected by a criterion..., measured by ...)",
or report the specific chart employed in case such sequences are not yet
available.  At any time reliable set of photometry is published
(on any literature or on any available online material), one can
introduce it as the standard system.  What a simple solution could it be!

> In the meantime, work progresses behind the scenes to reconcile the
> differences between existing AAVSO, BAAVSS and RASNZ sequences. A small
> group of determined and enthusiastic people are working out the parameters
> and guidelines for creating a 'global sequence database'. The ultimate goal
> being to have excellent sequences in a computer readable format that can be
> downloaded by everyone, in the chart scale, orientation and limiting
> magnitude of their choice. This information would also be available to sky
> charting software vendors.

   When these data become available, would it be an excellent idea to
put is as a standard public catalog at CDS (as an entry something like
"AAVSO Sequence of Comparison Stars for Visual Photometry").  The list of
Hubble exposures are registered in the same manner, and are regularly
updated.  The public availablity of the standard sequences in a similar
manner (not restricted to chart vendors) would merit every observer!

Regards,
Taichi Kato

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