Site testing campaign for the Large Optical Telescope at the Ali site

Abstract

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter telescope which is proposed to be built in western China. The site selection for LOT in China began in 2016, and Ali was listed as one of the three candidate sites. Remote studies and local surveys have been carried out for more than 15 years in western China, and the results show that Ali is a promising site with comprehensive quality in terms of atmospheric and supporting conditions. An overview of the site testing campaign at the Ali site from 2016 to 2019 is presented. After the two years of data collection, the overall median seeing value is found to be 1.17 arcsec, the observable nights are 81.71% and the good observable nights are 71.76%. The weather conditions as follows, the median night temperature value is –5.18°C, the median night relative humidity value is 41.25%, the median night atmospheric pressure value is 540.92 hPa, the median night wind speed value is 7.41 m s–1 and the mainly wind direction is southwestern (SW). The median night sky background value is 22.07 magV. We also discuss the wind speed at different locations on-site, the possibility of light pollution and the effect of wind speed on differential image motion monitor (DIMM) seeing measurements.

Screening Approach of the Langley Calibration Station for Sun Photometers in China

“…The Ali Astronomical Observation Station of the National Astronomical observatory is 5100 m above sea level, and it is located in the Tibetan Plateau region, where the air is dry, there are few clouds and little pollution, and the high altitude is potentially advantageous for infrared and submillimeter wave band observations [53]. It is a recently constructed observatory, following a long-term site survey in western China [54].…”

Report on seeing, sky brightness, and meteorological properties measurements at Timau National Observatory site

“…Seeing was measured using the Differential Image Motion Monitor (DIMM) method [8,9]. The DIMM method also widely used to characterize the seeing parameter such as in Ali and Muztagh-ata site in China [10,11] and Iranian National Observatory project at Mount Gargash [12]. Measurements were made using a telescope with a diameter of 20 cm with a focal length of 195 cm (f/9.75).…”