[vsnet-chat 706] Re: Charts and Sequences

[Taichi Kato <tkato>]

Roger Pickard wrote:

> This has been of concern to us all for a long time now, and some 
> discussion has already taken place between the AAVSO and the BAA VSSC, 
> but without, as yet, finding a suitable way forward.

   I think the process of (possible) standardization of variable star charts
consists of different sorts of steps.  Some may need international agreement,
but others may be only a matter of individual works.  I confine the discussion
to visual observations, only for simplicity.

   Possible list of processes may include:

  1) standardization of the appearance of the chart (eg. direction of the
     north, field of view, limiting magnitude etc.) -- should it be necessary?

  2) selection of the recommended comparison stars (should all variable star
     organizations use the same set of comparison stars or not)

  3) selection of the magnitude system (V-band, or something else?)

  4) works to obtain magnitudes of candidate comparison stars and previously
     used comparison stars, in some standard system (eg. V and B etc.), which
     enables transformation to whatever system is selected for visual
     observations in future

  5) works to convert previously obtained visual estimates to some standard
     system, or system (including labelling system) which enables future
     transformation to whatever system is selected

   I have a feeling the process 1), 2), 3) would probably require a more
elaborate international consortium on standardization of variable star
charts, while 4) or 5) may be achieved by volunteer works without waiting
for perfect agreements in other points.  Wouldn't it be an idea to adopt
a "metasystem" including V and at least one color (B-V, b-y or V-I etc.),
to find a way forward in 4) and 5)?  Labelling comparison stars would be
an easier task at the times of public availability of huge catalogs.

   I have also heard the ICQ recommends VT (V_T) values, rather than V,
when using Tycho catalogue, while I suspect the variable star community
seems to have reached at least a certain degree of consensus of using V
when using Tycho.  What about this?  Wouldn't it be a better for such a
consortium to cover different fields of visual astronomy?

Regards,
Taichi Kato

VSNET Home Page

Return to Daisaku Nogami

---

vsnet-adm@kusastro.kyoto-u.ac.jp