The Thirty Meter Telescope (TMT) is a proposed future generation telescope which will be located on either Maunakea, Hawaii or La Palma in the Canary islands. A thermal-infrared (TIR) imager and spectrometer (MICHI) combined with an adaptive optics system is being investigated as a possible second-generation instrument for this telescope. MICHI has been designed to also have a polarimetry capability in both imaging and low dispersion spectroscopic modes. Using polarization ray tracing in Zemax, we have estimated the instrumental polarization (IP) and crosstalk introduced at the focus of the near- and mid-infrared imaging system. In our calculations, we find that the IP varies from 1.0-0.54% and 0.54-0.42%, whereas the polarization crosstalk varies between 25-4% and 4-0.7%, in the near and TIR regions respectively at the instrument port of MICHI. These values of IP and crosstalk may cause problems during the high absolute accuracy polarization observations. Here we present the polarization effects for the imaging system of MICHI and it impacts on the polarization observations.
Initially the primary mirror of the 3.6m Devasthal Optical Telescope is uncoated polished zerodur glass supplied by Lytkarino Optical Glass Factory, Russia/Advanced Mechanical and Optical Systems, Belgium. In order to do the aluminium coating on the primary mirror the coating plant including washing unit is installed near the telescope (extension building of telescope) by Hind High Vacuum (HHV) Bangalore, India. Magnetron sputtering technique is used for the coating. Several coating trials are done before the primary mirror coating; samples are tested for reflectivity, uniformity, adhesivity and finally commissioned. The primary mirror is cleaned, coated by ARIES. We present here a brief description of the coating plant installation, Mirror cleaning and coating procedures and the testing results of the samples.
A 3.6m aperture telescope has been installed at Devasthal recently and once commissioned this would be the largest optical telescope in India. The integration of the telescope was carried out by lifting the components from inside the telescope building. To make this possible, the position of the telescope was shifted by 1.85m from the dome centre at an angle of 255 degree with respect to the north. This posed a serious challenge in synchronizing the dome with the telescope movement. In this contribution we will be presenting the synchronization algorithm and dome control software.