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Unformatted text preview: IMACS, the multi-object spectrograph and imager for Magellan: a status report Bruce C. Bigelow and Alan Dressler Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 ABSTRACT The Inamori Magellan Areal Camera and Spectrograph (IMACS) will soon be one of the three first-generation instruments for the Magellan 6.5m telescopes. This instrument drove the specification and design of the f/11 Gregorian focus on Magellan, which it uses to feed an all-spherical, refracting wide-field collimator with a 30 arcmin field of view. Two Epps cameras are used to re-image the field of view for imaging and spectroscopy. The aspheric, f/2 (“short”) camera images a field of 27 x 27 arcmin at 0.2 arcsec/pixel, and produces 0.32 arcsec images averaged over all field positions across the 0.39 –1.05 micron bandpass. The all-spherical f/4 (“long”) camera images a field 15 x 15 arcmin at 0.11 arcsec/pixel, and produces 0.16 arcsec images averaged over all field positions across the 0.365 – 1.0 micron bandpass. This paper describes the final specifications for the multiple spectrographic and imaging modes, and provides a status report on the current state of the instrument project. Keywords: MOS, spectrographs, optics, cameras, opto-mechanics, flexure control, 1. INTRODUCTION The IMACS (Inamori Magellan Areal Camera and Spectrograph) is the principal multi-object spectrograph and imager for the 6.5m Magellan I telescope. The five year, five million dollar project to build the instrument is in its final stages at the instrument laboratories of the Carnegie Observatories in Pasadena, Ca. This paper provides a status report for the instrument, and describes some of its features. See additional papers in these proceedings by Dressler 1 (target science for IMACS), Epps 2 (the optically athermalized f/2 camera), Bigelow 3 ( the CCD detector and dewar system), and Sutin 4 (echellette mode). Concurrently, the Observatories are in the final stages of construction for the telescopes and the first generation of optical and infrared instrumentation. See Shectman 5 for report about telescope project progress, and Bernstein 6 for a description of the MIKE double-echelle spectrograph. IMACS mounts at the Nasmyth focus of the Magellan I telescope. Fed by the f/11 Gregorian configuration (which will soon include an integral ADC and field corrector mounted at the tertiary mirror), the transmitting, all-spherical collimator produces a well corrected, unvignetted field of 24 arcmin in diameter, and a full 30 arcmin in diameter with slight vignetting. Two cameras are used to re-image the 150mm- diameter collimator exit pupil at 0.111 and 0.201 arcsec/pixel. The all-spherical, f/4 Epps “long” camera can directly image a 15 x 15 arcmin field of view (FOV), or spectroscopically image a 15 arcmin long slit with a variety of standard 150 x 200 mm diffraction gratings. The aspheric, f/2 Epps “short” camera can directly image a 27 x 27 arcmin FOV (with slight vignetting), or spectroscopically image a 27 arcmin long...
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This note was uploaded on 07/17/2008 for the course ASTRO 890 taught by Professor Martini during the Spring '08 term at Ohio State.
- Spring '08