Q-Spec: a concept for the Giant Magellan Telescope high resolution optical spectrograph

S. Barnes; P. MacQueen

doi:10.1117/12.787254

9 July 2008 Q-Spec: a concept for the Giant Magellan Telescope high resolution optical spectrograph

S. Barnes, P. MacQueen

Proceedings Volume 7014, Ground-based and Airborne Instrumentation for Astronomy II; 70141H (2008) https://doi.org/10.1117/12.787254
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

Abstract

Q-Spec is a concept for the Giant Magellan Telescope High Resolution Optical Spectrograph. It is a seeing limited, four channel spectrograph designed for high efficiency, high resolution spectroscopy from 305 to 1060 nm. Overall instrument dimensions are minimized with anamorphic preslit optics, pupil slicing, and white pupil beam demagnification. Q-spec uses two 300 × 1600mm R4 echelle grating mosaics of either 2 or 4 individual gratings, with 41.6 and 31.6 grooves/mm line densities. Two beam sizes are selectable in the preslit optics. A 450mm beam yields Rφ = 30,000 while a 900mm beam reaches Rφ = 60,000. Both beams are anamorphised before echelle dispersion, and the larger beam is pupil sliced. The post-echelle white pupil transfer optics demagnify the beam by 3. This allows the use of efficient vph grating cross-dispersers, and unvignetted f/1.5-2.0 dioptric cameras with optical element diameters under 250 mm. The bandwidth is split by a dichroic prior to the entrance slit, and by dichroics near the intermediate foci of the two sets of white pupil transfer optics. The four fixed spectral formats have 2-pixel resolving powers of ~200,000 and it is anticipated that resolving powers of R = 150, 000 or greater will be possible. The largest ccd is 6k × 6k with 15 μm pixels, and the minimum order separation is around 10 arcseconds. Q-spec can be fed with fibers in either multiple-object and/or precision radial velocity modes. Excluding the gravity-invariant thermal and vacuum enclosures, the instrument volume is a modest 5 × 2.5 × 2m in size.

Citation Download Citation

S. Barnes and P. MacQueen "Q-Spec: a concept for the Giant Magellan Telescope high resolution optical spectrograph", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70141H (9 July 2008); https://doi.org/10.1117/12.787254

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