3 Observations

The spectroscopic observations were collected as two 900 s exposures with FORS2 in MXU mode at VLT Kueyen (former UT2) on Paranal as part of the first commissioning period of the instrument. The instrument is described by Böhnhardt (2000), and Seifert et al. (2000), while the mask exchange unit (MXU) of FORS2 is described by Schink et al. (2000). The nominal pointing was RA = 00:56:19.043, DEC = -72:27:59.81 for the instrument setup. Up to 7 reference stars were used to align the telescope pointing to the correct position. Additionally a reference slit was specified to correct the image flexure of the instrument. The wavelength range coverage is 6533Å $< \lambda <$ 6593Å. Most of the slits were longer than 8 arcsec, providing sufficient sky background. Some slits were occupied with two or more targets. Four slits were inclined with respect to the dispersion direction to optimize the sky background region and the spectra required an additional row-by-row alignment handling using the wavelength calibration. The log of observations is given in Table 1. Thanks to the negligible image flexure of FORS2 calibration frames could be collected a day earlier during day-time with the telescope in zenith position.

 

 

Table 1: Log of observations. From left to right: Julian date, date and UT at start of observation, FORS2 instrument modus, grism, interference filter and central wavelength, exposure time, approximative seeing and air mass

JD	date	UT	mode	grism	filter	$\lambda_{\rm c}$	time	seeing	X
						nm	sec	arcsec
2451494.15	12/11/99	03:38	MXU	600R+24	H_Alpha+59	656	900	0.8	1.5
2451494.16	12/11/99	03:54	MXU	600R+24	H_Alpha+59	656	900	0.8	1.5