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1.3m Telescope at Devasthal (Telescope Parameters)
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130-cm diameter optical telescope has been installed in December 2010 at Devasthal, Nainital in the central Himalayan region. The main objective for setting up of a 130 cm optical telescope at Devasthal was to meet the observational requirements for the institute's scientific programs, which were so far being carried out using nearly 40 year old 104-cm Sampurnanand telestcope. The institute's main scientific programs such as monitoring of transients (Gamma Ray Bursts; GRB, Supernovae explosions), variability of stars in the Milky-way and of active nucleus in external galaxies require an automated telescope for efficient observations. Other programs such as imaging of star clusters require wide field imaging capabilities. The installed 130-cm telescope at Devasthal is able to fulfill most of the these requirements.
The telescope has been fabricated by DFM Engineering Inc. USA. The telescope uses a modified Ritchey-Chretien Cassegrain design and the focal length to diameter ratio (focal-ratio) of the overall optics was kept at 4 making it a very fast system providing 40 arcsec view of the sky in 1 mm scale at the focal plane. A single element corrector provides a nearly flat field view of the sky up to 66 arcmin in diameter.
The tube of the 130-cm telescope is of open truss allowing the telescope to cool faster in the ambient. The telescope mount is of fork-equatorial type. The telescope can be pointed to a celestial object with an accuracy of 10 arcsec rms. The mechanical system provides a tracking accuracy at nearly 0.5 arcsec rms over 10-min without any external guider. The images obtained with the telescope show best FWHM at nearly 1 arcsec. The atmospheric extinction at Devasthal is measured as 0.24 mag in B (Blue), 0.14 mag in V (Visual), and 0.08 mag in R (Red) band on the first week of December, 2010. The sky brightness is measured as 21.2 mag/arcsec2 in the V band in moonless night.