[vsnet-chat 5162] Re: About courios observation, big confusion

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

Re: [vsnet-chat 5158] About courios observation, big confusion

   Another point of this curious observation:

> fainter then  magMin 10.5 p of  HYAFH and brigther then 12.2 of GSC4900:329.
> If need I will send the images.
> 
> On the other hand, on images, the star appear of orange coulor and
> comparison with the near star
> GSC 4900:477 9.8/0.4 and GSC 4900:491 10.3/0.4, the different magnitude is
> well visible.

   It is likely your photometry program used GSC magnitudes as a reference.
It is well-known that most of southern GSC magnitudes are from blue-sensitive
plates, which usually give systematically fainter magnitudes.
Since the object is bright enough, you must have enough number of Tycho-2
stars, which have much reliable magnitudes.  In case your software doesn't
support this (or other photometric) catalog, it would be better to discard
it for future photometry.

Regards,
Taichi Kato

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