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(1993 Apr. 11)
subject: discrepancies between mv and V
Sir Dr. Gerard de Vaucouleurs,
During the course of compilation of the photometry table, there
arose possible explanation of discrepancies between visual and V
magnitudes early in the initial decay.
At that time, the magnitudes of the comparison stars close to
the supernova had not been determined. Together with the brightness
of the supernova, the observers (especially TB chart users) were
obliged to use distant comaprisons. The magnification would be
low then, therefore the magnitudes of the supernova may be affected
by the local galaxy background, i.e. tends to be bright. Visual
observers know such false variability are met in nebulosity like
variable stars in the Orion nebula.
After the magnitudes (even in the preliminary sense) of the
local comparisons (A,B) were determined, the estimated magnitudes
very well represent V magnitudes. I have been receiving inidividual
estimates with comarisons used, step values etc. necessary for
further analysis.
Therefore the discrepancy may not be so strange if we take
account of the absence of local comparisons and the effect of
galaxy background. Observations of mentioned condition (telescope
size, comparisons, magnifications etc.) may be properly corrected
in future works.
Regards,
Taichi Kato
Return to the Powerful Daisaku Nogami
vsnet-adm@kusastro.kyoto-u.ac.jp
