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Дата изменения: Sat Nov 25 17:34:14 2000
Дата индексирования: Sat Sep 11 20:29:20 2010
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Поисковые слова: comet tail

Observations

All results presented below have been obtained by observations with the Russian 6m telescope, mainly in the snap-shot mode during 4 runs between December 1998 and February 2000. The spectrograph SP-124 attached to the Nasmyth-1 focus of the telescope was used during the first run. We used a grating with 300 grooves/mm (see log of observations in Table 2) and a long slit of 2$\times$40. The scale along the slit was 0.4/pixel.

The Long-Slit Spectrograph (LSS in Table 2) (Afanasiev et al. [1995]) attached to the telescope prime focus was used during the remaining 3 runs. Most of the long-slit spectra (12-20$\times$180) were obtained with a grating of 325 grooves/mm, giving a dispersion of 4.6 Å/pixel. Additional data were obtained with a grating of 650 grooves/mm giving a dispersion of 2.4 Å/pixel. The scale along the slit was 0.39/pixel. For all observations we used the Photometrics CCD-detector PM1024 with $24\times24\mu$m pixel size.

Normally, short exposures were used (2-5 minutes) in order to detect strong emission lines, to measure redshifts and make a first classification. Reference spectra of an Ar-Ne-He lamp were recorded before or after each observation to provide a wavelength calibration. Spectrophotometric standard stars from Oke ([1990]) and Bohlin ([1996]) were observed for flux calibration at least twice a night. All observations and data acquisition have been conducted under the NICE software package by Kniazev & Shergin (1995) in the MIDAS environment.

Part of the second priority candidates was observed with the 2.2m telescope on Calar Alto in June 1999. These observations will be presented in a forthcoming paper, although we will make use of the results in our analysis below.