[vsnet-obs 18110] Re: (fwd) SN1998es photometry and astrometry (Sala)

["Giuseppe A. Sala" <g.sala@skylink.it>]

At 21.26 20/11/98 -0700, Brian Skiff wrote:
>     The USNO-A series magnitudes are usually somewhat too bright for both
>the blue and red magnitudes, but there is wide variation from field to
>field.  This is almost certainly the source of the problem with Dr. Sala's
>SN magnitude.  In any case, without proper calibration directly in the
>field, setting zero-points in unfiltered CCD images is not really possible.
>Dr. Sala may wish to also image the nearby GSPC field (about 1.5 degrees
>from the supernova), and compare the magnitudes he gets from 'Astrometrica'
>with the true V and B-V values.  He may get a surprise!
>     I am observing tonight at the Lowell 1.1-m telescope, and plan to 
>obtain BVR photometry in the field of NGC 632 in a little while.
>
>\Brian


Thanks for your remarks and suggestions. A quick photometry in the field
(same CCD image used before) by using GSC 34:422 (14.0) as reference star
gives m=14.1 for sn1998es! Just learning ...

\Giuseppe



*****************************
Dr. Giuseppe Arnaldo Sala
e-mail:g.sala@skylink.it 
e-mail:g.sala@starlight-xpress.com 
Starlight Xpress Systems <http://vsnet.starlight-xpress.com>
CCD Astronomy Research Centre
27, Via Cottalorda
21022 Azzate (VA), Italy
Tel/Fax +39-332-459825
Mobile Phone:+39-347-236-9736
International Supernova Network:
<http://vsnet.supernovae.org/isn.htm>

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