[vsnet-chat 1845] Re: [vsnet-chart 151] Chart of SN1999by

[Taichi Kato <tkato>]

Re: [vsnet-chart 151] Chart of SN1999by

>      Was the BVRI sequence I sent out earlier not suitable for getting as
> better zero-point in the NGC 2841 field using USNO-A stars?

    The USNO magnitudes seem to be considerably affected by the galaxy
background and/or poor zero-point calibration.  For example, NGC 2841 2
(V=11.07) in Brian's list has a USNO magnitude of 12.85.  I don't judge
whether such a large zero-point correction can by applicable in this
case, and strongly urge observers to use the BVRI sequence for comparison.
(I hope someone can extend the sequence as soon as possible, since there
is a large gap between mag 11.07 and 13.51).

Regards,
Taichi Kato

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