International Journal of Astronomy and Astrophysics, 2013, 3, 376-384 Published Online December 2013 (http://www.scirp.org/journal/ijaa) http://dx.doi/org/10.4236/ijaa.2013.34043 Open Access IJAA Optical Spectrometer with Acousto-Optical Dynamic Grating for Guillermo Haro Astrophysical Observatory Alexandre S. Shcherbakov, Adán Omar Arellanes, Vahram Chavushyan National Institute for Astrophysics, Optics & Electronics (INAOE), Puebla, Mexico Email: alex@inaoep.mx, arellaneso@inaoep.mx, vahram@inaoep.mx Received August 23, 2013; revised September 12, 2013; accepted September 19, 2013 Copyright © 2013 Alexandre S. Shcherbakov et al. This is an open access article distributed under the Creative Commons Attribu- tion License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Optical spectrometer of the Guillermo Haro astrophysical observatory (Mexico) realizes investigations in the visible and near-infrared range 350 - 800 nm and exploits mechanically removable traditional static diffraction gratings as dis- persive elements. There is a set of the static gratings with slit-densities 150 - 600 lines/mm and optical apertures 9 cm × 9 cm that provide the first order spectral resolution from 0.8 to 3.2 Å/pixel, respectively. However, the needed me- chanical manipulations, namely, replacing the static diffraction gratings with various resolutions and following recali- bration of spectrometer within studying even the same object are practically inconvenient and lead to wasting rather expensive observation time. We suggest exploiting an acousto-optical cell, i.e. the dynamic diffraction grating tunable electronically, as dispersive element in that spectrometer. Involving the acousto-optical technique, which can potentially provide electronic control over the spectral resolution and the range of observations, leads to eliminating the above- mentioned demerits and improving the efficiency of analysis. Keywords: Optical Spectrometer; Acousto-Optical Cell; Dynamic Diffraction Grating; Acousto-Optical Material; Schematic Arrangement; Spectral Resolution; Efficiency of Spectrum Analysis 1. Introduction: General Characterization of the Spectrometer The Cassegrain telescope, which is in operation at the Guillermo Haro astrophysical observatory (Mexico), in- cludes classical static grating spectrometer (from Boller & Chivens Corp.). Presently, this spectrometer is availa- ble on the observatory at the 2.12-meter telescope with 5 static diffraction gratings, see Table 1. All the static gra- tings are 9 cm × 9 cm in size, and they are exploited in the first order of light diffraction with the dispersions ranging from 450 to 114 1 Å mm   , allowing a good coverage in both dispersion and wavelength within the CCD matrix photodetector sensitivity ranges. The use of acousto-optics techniques in astronomy starts from the late 1960s when a new kind of spectral devices were de- veloped, electronically tunable acousto-optical filters (AOFs). Later, in the middle of the 1970s [1], the first efforts to use the tunable AOFs for astronomical spec- troscopic observations were made at the Harvard Obser- vatory in 1976. Using a collinear filter is based on cal- cium molybdate crystal. Conceptually and technologically, Table 1. Static diffraction gratings available in the Guiller- mo Haro astrophysical observatory. Slit-density (lines/mm) Blaze wavelength (Å) Resolution (Å/pixel) 150 5000 3.2 300 5000 1.6 300 7500 1.6 600 7500 0.8 600 4850 0.8 AOFs at that time were imperfect. The filter had a small optical aperture (4 × 4 mm) and a large interaction length   ~50 mm . Now, the tunable AOFs are technologically mature, compact tunable AOF-based spectrometers and cameras are widely used for research and process control. For example, acousto-optics is widely used currently for spectroscopy in radio-astronomy. In 2002, imaging spec- trophotometer on optical range with CCD cameras was tested [2]. More examples exist for the use of acousto- optics in astrophysical spectroscopy, such as SPICAM in