2 Observations

Unfiltered CCD observations were carried out at Piszkésteto Station of Konkoly Observatory on six nights from January, 1998 to April, 1998. The instrument used was the 60/90/180 cm Schmidt-telescope equipped with a Photometrics AT200 CCD camera ($1536\times 1024$ KAF 1600 MCII coated CCD chip). The projected sky area is $29'\times 18'$ which corresponds to an angular resolution of 1$.\!\!^{\prime\prime}$1/pixel. Although we did not use standard filters, the magnitude measurements fall close to R values based on the spectral sensitivity of the chip (Kelemen 1997).

We made $R_{\rm C}$ filtered observations with the same instrument on three nights between October 22 and October 26, 1998. Unfortunately other filters were not available during this observing run and consequently we could obtain only intrumental differential R magnitudes in respect to closely separated comparison stars.

The exposure times were limited by two factors: firstly, the asteroids were not allowed to move more than the half of the FWHM of the stellar profiles (varying from night to night) and secondly, the signal-to-noise (SN) ratio had to be at least 10. This latter parameter was estimated comparing the peak pixel values with the sky background during the observations. The journal of observations is summarized in Table 1.

  

Table 1: The journal of observations. (r - geocentric distance; $\Delta$ - heliocentric distance; $\lambda$ - ecliptic longitude; $\beta$ - ecliptic latitude; $\alpha$ - solar phase angle; aspect data are referred to 2000.0)

The image reduction was done with standard IRAF routines. The relatively high electronic noises and low angular resolution did not permit the use of psf-photometry and that is why a simple aperture photometry was performed with the IRAF task noao.digiphot.apphot.qphot. The applied differential photometry consisted of using a comparison and a check star close to the asteroid. The precision was estimated with the rms scatter of the comp.-check magnitudes (tipically 0.01-0.03 mag). The presented magnitudes throughout the paper are based on magnitudes of the comparison stars taken from the Guide Star Catalogue (GSC). Therefore, their absolute values are fairly uncertain (at level of $\pm~0.2-0.3$ mag). Fortunately this is a less significant factor, since it does not affect the main photometric parameters needed in the minor planet studies, such as the amplitude, or photometric period. The final step in the data reduction was the correction for the light time.

Composite diagrams were calculated using APC11 by Jokiel (1990) and are also light time corrected. Times of zero phase are included in the individual remarks.