[vsnet-sequence 135] Re: [vsnet-chat 5181] Charts and sequences

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

Re: [vsnet-chat 5181] Charts and sequences

Sebastian,

> 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??

    I believe you are perfectly correct.  The quality of comparison stars
little vary as long as chart-makers insist on this (now widely available)
standard system.  Only a few problem of selection come from the range of
color indexes (I prefer to use 0 < B-V < +1 stars, because they are less
affected by personal bias), treatment of double or multiple stars
(e.g. the recent problem of delta Sco comparison star).

    However, this is not true in some cases.  Some star chart programs
display GSC magnitude as their primary "standard" system, and star-chart
mappers often use them...  Some observers apparently rely on SAO to get
"V" magnitudes...  Confusion between Hipparcos (Hp), Tycho (VT) natural
systems with the standard V system is also widely encountered.
Even in the presence of this knowledge, the recent example of U Gem AAVSO
chart clearly demonstrate how difficult it is to convince everyone
of the importance of the standard system.

Regards,
Taichi Kato

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