28 July 2014 SPRAT: Spectrograph for the Rapid Acquisition of Transients
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We describe the development of a low cost, low resolution (R ~ 350), high throughput, long slit spectrograph covering visible (4000-8000) wavelengths. The spectrograph has been developed for fully robotic operation with the Liverpool Telescope (La Palma). The primary aim is to provide rapid spectral classification of faint (V ∼ 20) transient objects detected by projects such as Gaia, iPTF (intermediate Palomar Transient Factory), LOFAR, and a variety of high energy satellites. The design employs a volume phase holographic (VPH) transmission grating as the dispersive element combined with a prism pair (grism) in a linear optical path. One of two peak spectral sensitivities are selectable by rotating the grism. The VPH and prism combination and entrance slit are deployable, and when removed from the beam allow the collimator/camera pair to re-image the target field onto the detector. This mode of operation provides automatic acquisition of the target onto the slit prior to spectrographic observation through World Coordinate System fitting. The selection and characterisation of optical components to maximise photon throughput is described together with performance predictions.
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A. S. Piascik, A. S. Piascik, Iain A. Steele, Iain A. Steele, Stuart D. Bates, Stuart D. Bates, Christopher J. Mottram, Christopher J. Mottram, R. J. Smith, R. J. Smith, R. M. Barnsley, R. M. Barnsley, B. Bolton, B. Bolton, "SPRAT: Spectrograph for the Rapid Acquisition of Transients", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91478H (28 July 2014); doi: 10.1117/12.2055117; https://doi.org/10.1117/12.2055117

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