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Дата изменения: Tue Feb 8 09:57:26 2000
Дата индексирования: Sat Sep 11 20:33:11 2010
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Поисковые слова: туманность андромеды

Observations with the KPNO 2.1m telescope

The observations were made with the GoldCam spectrograph used in conjunction with the 3K$\times$1K CCD detector. We used a 2''$\times$229'' slit with the grating 09 (316 grooves mm^-1) in its first order, and a GG 375 order separation filter. This filter cuts off all second-order contamination for wavelengths blueward of 7400Å which is the wavelength region of interest here. This instrumental set-up gave a spatial scale along the slit of 075 pixel^-1, a scale perpendicular to the slit of 2.7Å pixel^-1, a spectral range of 3500-7500Å and a spectral resolution of $\sim$ 5Å. These parameters permitted to cover simultaneously the blue and red spectral range with all the lines of interest in a single exposure and with enough spectral resolution to separate important emission lines as H$\gamma$ $\lambda$4340 and [O III] $\lambda$4363, and H$\alpha$ $\lambda$6563 and [N II] $\lambda$6584. Normally, short exposures were used (5 minutes) in order to detect strong emission lines, to measure redshifts and make some crude classification.

Reference spectra of an Ar-Ne-He lamp were recorded to provide a wavelength calibration. The spectrophotometric standard star Feige 34 from Massey et al. ([1988]) was observed for the flux calibration at least once a night. No effort was made to orient the slit along the parallactic angle, so line flux ratios could be spectrophotometrically inaccurate. The observations were complemented by dome flats, bias-, and dark frames. The seeing was about 3$\arcsec$(FWHM).