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Дата изменения: Fri Jun 8 14:28:15 2001
Дата индексирования: Sat Sep 11 20:24:44 2010
Кодировка:
Поисковые слова: mercury surface

Observations with the KPNO 4m telescope

The observations were carried out with the Ritchey-Chretien Spectrograph attached to a Tektronix 2K$\times$2K CCD detector. We used a 2''$\times$205'' slit with a KPC-10A grating (316 grooves mm^-1) in its first order, and a GG 375 order separation filter cutting off second-order contamination for wavelengths blueward of 7400Å. This instrumental setup allows a spatial scale along the slit of $0\farcs69$ pixel^-1, a scale perpendicular to the slit of 2.77Åpixel^-1, a spectral range of 3700-8300Å and a spectral resolution of $\sim$ 7Å (FWHM). Short exposures (3-5 minutes) were used in order to detect strong emission lines to allow measurement of redshifts and a crude classification. No orientation of the slit along the parallactic angle was done because of the snap-shot observing mode. Reference spectra of an Ar-Ne-He lamp were recorded to provide wavelength calibration. Spectrophotometric standard stars from Oke ([1990]) and Bohlin ([1996]) were observed at the beginning and at the end of each night for flux calibration. The dome flats, bias, dark and twilight sky frames were accumulated each night. The weather conditions were photometric, with seeing variations between 25 and 3 (FWHM).