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Proceedings Paper

Multi-object spectroscopy on the Hobby-Eberly Telescope low-resolution spectrograph
Author(s): Marsha J. Wolf; Gary J. Hill; Wolfgang Mitsch; Frederic V. Hessman; Werner Altmann; Keith L. Thompson
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Paper Abstract

The low resolution spectrograph (LRS) is the first facility instrument on the 9.2m Hobby-Eberly Telescope (HET). The LRS has three operational modes: imaging, long-slit spectroscopy and multi-object spectroscopy (MOS). We present the design and early operations performance of the LRS MOS unit, which provides 13 slitless, each 1.3 arcsec by 15 arcsec, on 19.6 arcsec centers, within the 4 arcmin field of view of the HET. This type of remotely configurable unit was chosen over the more conventional slit masks due to the queue scheduling of the HET, and the instrument's remote location at the prime focus of the telescope. A restricted envelope around the HET focus at the LRS port forced a very compact design. The MOS unit has miniature mechanisms base don custom cross- roller stages and 0.25 mm pitch lead-screws. Geared stepper motors with 10 mm diameters drive the 13 axes at 0.8 micron per step. The precision of the mechanism is far greater than required by the HET plate scale of 205 microns per arcsec, but result in a robust unit. The slitlets were fabricated at the University of Texas by shadow-masking the slit area with a wire and vacuum depositing aluminum onto the silica substrates. Both sides are then coated with MgF2 which serves as an antireflection coating and a protective layer. Web-based software is available for optimizing the orientation of the MOS unit and the placement of slitlets on objects in the field. These setup scan be down loaded to the unit for configuration outside of the beam while the HET is slewing to its next target in the queue, or while the LRS is used in imaging mode for setup on faint objects. The preliminary results presented here are from one commissioning run with the MOS, where the unit appears to be meeting performance specifications.

Paper Details

Date Published: 16 August 2000
PDF: 12 pages
Proc. SPIE 4008, Optical and IR Telescope Instrumentation and Detectors, (16 August 2000); doi: 10.1117/12.395476
Show Author Affiliations
Marsha J. Wolf, McDonald Observatory/Univ. of Texas at Austin (United States)
Gary J. Hill, McDonald Observatory/Univ. of Texas at Austin (United States)
Wolfgang Mitsch, Universitaets-Sternwarte Muenchen (Germany)
Frederic V. Hessman, Universitaets-Sternwarte Goettingen (Germany)
Werner Altmann, Konstructionsbuero Werner Altmann (Germany)
Keith L. Thompson, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 4008:
Optical and IR Telescope Instrumentation and Detectors
Masanori Iye; Alan F. M. Moorwood, Editor(s)

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