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20 July 2010 The design of dispersing elements for a highly segmented, very wide-field spectrograph
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Wide field spectrograph at the largest optical telescopes will be decisive to address the main open questions in modern astrophysics. The key feature of this instrument is the modular concept: the spectrograph is the combination of about one thousand identical small cameras, each carrying a few slits and operating at low to moderate spectral resolution, to be illuminated at the Cassegrain focus of an existing 8m class telescope. The dispersing element to be used in these small cameras has to satisfy some requirements in term of efficiency, resolution, size, small series production. Moreover the cameras have to work both in imaging and spectroscopy modes, therefore a GRISM configuration of the dispersing element is suitable. Based on these considerations, we have focused our attention to Volume Phase Holographic Gratings (VPHGs) since they show large peak efficiency in the target spectral range (400-800 nm), they can be arranged in a GRISM configuration reaching relative large resolution. The main constrains concern the available room for the dispersing element, indeed the camera design is very compact. As a consequence, slanted VPHGs are studied and optimized in combination with normal and Fresnel prisms.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Andrea Bianco, Dario Maccagni, Roberto Ragazzoni, Adriano Fontana, Andrea Baruffolo, Marco Dima, Andrea Di Paola, Jacopo Farinato, Giorgia Gentile, Emanuele Giallongo, Demetrio Magrin, Fernando Pedichini, Roberto Speziali, and Vincenzo Testa "The design of dispersing elements for a highly segmented, very wide-field spectrograph", Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 77357M (20 July 2010); doi: 10.1117/12.857689;


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