The Ohio State Multi-Object Spectrograph

Abstract

The Ohio State Multi-Object Spectrograph is a new wide-field imager andmultiobject spectrograph for the 2.4 m Hiltner Telescope at the MDMObservatory. OSMOS has an all-refractive design that reimages a 20'diameter field of view onto the 4064 x 4064 MDM4K CCD with a plate scaleof 0.273 `' pixel(-1). Approximately an 18.5' square region of thisfield illuminates the detector and is available for spectroscopy,although with reduced wavelength coverage near the edges of the field.Slit masks, filters, and dispersers are all mounted in a series ofsix-position aperture wheels. These mechanisms rotate between positionsin only a few seconds; consequently, the instrument may be rapidlyreconfigured between imaging and spectroscopic modes. At present, alow-resolution triple prism (R similar to 60-400) and amoderate-resolution volume-phase holographic grism (R similar to 1600)are available.