A Telescope That Scans in Bulk
In the Yan Mountains of Hebei province, about 150 km from Beijing, Xinglong National Observatory operates the largest optical observatory in Asia. Founded in 1968, the station is at an altitude of about 900 meters and has nine telescopes with apertures over 50 cm. The main instrument at the site is the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), also called the Guo Shoujing Telescope.
LAMOST has a unique design, functioning as a reflecting Schmidt telescope with active optics. Its primary mirror has an effective aperture of about 4 meters. This design provides a very wide field of view, covering 5 degrees of the sky. The telescope feeds light from up to 4,000 celestial objects simultaneously into 16 spectrographs using optical fibers. This capability makes it the world's most efficient telescope for acquiring spectral data, capturing tens of thousands of spectra in a single night. Since its regular survey began in 2012, LAMOST has collected millions of spectra from stars and galaxies, used for studies on the structure of the Milky Way.
Legislating Darkness
The quality of astronomical observation depends heavily on atmospheric stability, known as "seeing," and the darkness of the night sky. Xinglong is located near major urban centers like Beijing and Tangshan, which create significant light pollution. To protect the observatory's scientific mission, the regional government enacted specific legislation to create a dark sky protection zone around the facility. While other dark sky preservation areas have been established in China, such as in Lenghu on the Tibetan Plateau, Xinglong's proximity to a major metropolis makes its protection effort particularly notable.
Atmospheric monitoring at Xinglong shows a median seeing value of around 1.7 to 1.9 arcseconds. The sky brightness at the zenith is approximately 21.1 mag/arcsec² in the V-band. These conditions, secured by legal protection against light pollution, allow for approximately 117 photometric and 230 total observable nights per year. The site's main workhorse before LAMOST was the 2.16-meter optical telescope, installed in 1974, which itself was a milestone in Chinese-built astronomical instruments.