[vsnet-chat 711] Re: Charts and Sequences

[Seiichi Yoshida <seiichi@muraoka.info.waseda.ac.jp>]

Hello.

Dr. Taichi Kato:
>    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?

The reason ICQ recommend VT rather than Johnson V is that the Johnson
V is not a value measured by observation but one converted by a
complex formula. If the color index is large, the error will be also
large. That's the reason I guess.

I also proposed to adopt the USNO catalog as one of a regular source
catalog for magnitude observations of comets. At the same time I
introduced the convertion formula by Dr. Kato:

> I have derived a tentative equation V = r + 0.375*(b-r) for b and r

but I heard that ICQ rejects it. So now comet observers cannot refer
to the USNO catalog. When a more reliable convertion formula is
determined, the situation may be changed. 

Regards,

--
Seiichi Yoshida
Muraoka Lab., Waseda University, Japan
seiichi@muraoka.info.waseda.ac.jp
http://vsnet.info.waseda.ac.jp/muraoka/members/seiichi/index.html

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