The New Multifunctional Spectrograph at the Bosque Alegre Station

Abstract

The new observational facility available at Bosque Alegre Station (Córdoba Observatory, ARGENTINA) is described. The spectrograph is mounted on the 1.54m Nasmyth reflector. The detector is a CCD camera (Photometrics AT 200), equipped with a 1024×1024 chip (Thomson CH 7896). The deviations from linearity of response are below 0.1%, the readout noise is 4 electrons pixel^-1 and the dark noise is about 6 electrons pixel^-1 hour^-1. The quantum efficiency of the camera has a 45% peak in 650nm and is enhanced in the blue by a Metachrome II coating. The spectrograph consists of a Maksutov-type collimator system of 600mm focal length (f/12) and an apochromatic camera lens of 200mm focal length (f/3.5). The pixel size projected onto the sky is 0.38“, which corresponds to an equivalent focal length of 10.38m. Three gratings are available for the spectroscopic modes: 300 g/mm, 600 g/mm and 1,200 g/mm. This spectrograph is of a modular design, intended to allow different configurations and observing modes during the same night. The configurations available, either imaging or spectroscopic, are:

• direct image, with the possibility of using coloured or interference filters, field of view: 5.7 x 5.7 arcmin

• multi-pupil image with lens array (by using field-pupil inversion), with or without filters

• long-slit grating spectroscopy, slit length: 4 arcmin on the sky

• integral field spectroscopy, with grating and lens array (Tiger type, Courtés 1980)

• two-dimensional, scanning Fabry-Pérot spectrometry (high spectral resolution) (Cigale type, Boulesteix et al. 1984)

• cross-dispersion (Fabry-Pérot + grating) spectrometry (high spectral resolution) (Pytheas type, le Coarer 1992)

• Echelle spectroscopy (high spectral resolution).