Lenghu Site

The Lenghu astronomical site is located near Lenghu Town, Mangya City, Qinghai Province, at an elevation of about 4,200 meters. It has been identified as one of the key high-altitude observing sites in western China. Several telescope platforms are under construction, and the Tianyu telescope is planned to be stationed here. The region offers a dry climate, low turbulence, and very good seeing, providing favorable conditions for high-precision optical surveys.

Advantages of High-Altitude Observing

• Reduced Air Mass: the 4,200 m altitude significantly reduces atmospheric scattering and absorption;
• Low Water Vapor: nighttime precipitable water vapor can be very low, benefiting optical and infrared work;
• Excellent Seeing: site-testing campaigns report median seeing around ~0.75 arcsec;
• High Clear-Night Fraction: more than 270 clear nights per year, ideal for long time-series monitoring.

Environment and Infrastructure

The Saishiteng mountain area near Lenghu provides relatively gentle high-plateau terrain suitable for standardized telescope platforms. Recent improvements in road access and power infrastructure, together with multiple ongoing telescope projects, enable coordinated observations and multi-wavelength campaigns.

Astronomical Suitability and Role of Tianyu

Lenghu has been evaluated to offer internationally competitive optical observing conditions, well suited for wide-field, high-cadence survey facilities. The Tianyu telescope will take advantage of this site to conduct long-term time-domain monitoring of exoplanets, transients, and variable stars, providing a stable data stream and technical testbed for time-domain astronomy in China.