The observations were carried out on different nights of September-October
1996 using the 90 cm telescope at Sierra Nevada Observatory, Spain.
This telescope is equipped with a six channel uvby
photometer for
simultaneous measurements in uvby or in the H
channels respectively
(Nielsen 1983), but only uvby measurements were collected during this
observing run.
In order to make differential photometry, the comparison stars were chosen
taking into account their spectral type (close to solar) and in
the neighbourhood of the asteroids for better reduction of the data avoiding
extinction problems.
C1=SAO 92273 (
,
K0) was used as the
main comparison star and C2=SAO 92119 (
,
G0),
C3=SAO 92152 (
,
G5) and C4=SAO 74083 (
,
A2) as check stars.
During the observations reported
here, neither of the comparison stars showed any sign of variability within
.
To transform our data into the standard uvby system, we have used the same procedure
described in Rodríguez et al. (1997).
After differential magnitudes in the standard system were obtained
for the asteroids with respect
to the main comparison star (C1=SAO 92273), we correct them to unit
distance from the sun and
the earth and perform light-time corrections to all the
observations.
Then, we transform these differential magnitudes to absolute magnitudes using
the standard values of C4,
,
,
and
,
listed in the Hauck &
Mermilliod (1998) catalogue.
In addition, we obtained the following values of
,
,
for C1, C2 and C3, respectively.
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