Sensitivity of 3.6m Devastal Optical Telescope

Abstract

The 3.6m optical telescope, currently the largest optical telescope in India is being built at Devasthal with an aim to develop an observational facility with spectral and seeing limited imaging capabilities at visible and near infrared bands. Electromagnetic radiation received on Earth are the major carriers of cosmological information. The ability of a telescope to collect the least possible signal describes its sensitivity. The aim of the project was to characterize the photometric and spectroscopic sensitivity of this telescope. A measure of sensitivity is given by the signal to noise ratio of the telescope. The signal to noise ratio for imaging as well as spectroscopy at various zenith angles and observing conditions has been calculated using MATLAB. In imaging, a signal-to-noise ratio of 3.9 has been obtained for a 25mag point source in V band, measured at zenith for an exposure time of 30 minutes, using a 4KX4K CCD camera with a pixel size of 15microns,three days from New Moon. And, in spectroscopy, a signal to noise ratio of 7.5 has been obtained for a 20 mag point source at 0.5 μm, measured at zenith for an exposure time of 10 minutes.