Solar Astronomy at High Altitude

Abstract

A major project called the National Large Solar Telescope (NLST) has been proposed for pursuing Solar Astronomy at High Altitude. The project envisages the development of a state-of-the-art 2-m class telescope to carry out high-resolution studies of the solar atmosphere. This project is led by the Indian Institute of Astrophysics and has national and international partners. Its geographical location will fill the longitudinal gap between Japan and Europe and is expected to be the largest solar telescope with an aperture larger than 1.5 m till ATST and EST come into operation. NLST is an on-axis alt-azimuth Gregorian multi-purpose open telescope with the provision of carrying out nighttime stellar observations using a spectrograph at the Nasmyth focus. The telescope utilizes an innovative design with low number of reflections to achieve a high throughput and low polarization. High order adaptive optics is integrated into the design that works with a modest Frieds parameter of 7-cm to give diffraction limited performance. The telescope will be equipped with a suite of post-focus instruments including broad and narrow band imagers, a high-resolution spectrograph and a polarimeter. A comprehensive site characterization programme has demonstrated the presence of at least two excellent sites for setting up observational facilities for solar astronomy at high altitude in India.

National Large Solar Telescope

“…Site characterization for NLST has been carried out at the following three sites in North India: Hanle and Merak in Ladakh (Jammu and Kashmir) since 2007 and at Devasthal (Uttarakhand) since 2009 using a Solar Differential Image Motion Monitor (SDIMM), Shadow Band Ranger (SHABAR), automatic weather station (AWS), all-sky camera, an automatic sky radiometer and a micro-thermal data acquisition system, designed and built in-house 8 . The main parameters chosen for the study were the total annual sunshine hours, sky brightness, atmospheric seeing at various heights above the ground, microthermal conditions, and some additional meteorological parameters such as wind speed, aerosol distribution, etc.…”