Huairou Solar Observing Station (HSOS) is one of the key stations of the National Astronomical Observatories, Chinese Academy of Sciences. It was built in 1984 and is located on an island near the north bank of the Huairou reservoir, 60 km north to the downtown of Beijing. The main scientific objective of the station is to measure and study the solar magnetic and velocity fields at various altitudes of the solar atmosphere.

Several advanced instruments are equipped on the station. The main telescopes are as follows.
(1)35-cm Solar Magnetic Field Telescope. The photospheric and the chromospheric vector magnetic fields as well as the line-of-sight velocity fields, at FeI 5324.19 Å and H_β4861 Å lines respectively, can be obtained by the system.
(2)60-cm Solar three-Channel Telescope. The monochromatic images and the vector magnetic fields can be obtained simultaneously at three spectral lines (MgI5173 Å, FeI5247 Å, FeI5250 Å).
(3)Monitor System of Solar Activity. It consists of two telescopes. One is a 10 cm full-disk vector magnetograph that measures the full-disk vector magnetic field at FeI 5324.19 Å. The other is a 20-cm Full-disk Hα telescope that obtains full-disk Hα monochromatic images.

HSOS is also involving in promoting the next generation of big telescopes in China, the Chinese Giant Solar Telescope (CGST) and the Deep-space Solar Observatory (DSO) for example. With a spatial resolution equivalent to an 8m telescope in diameter and a light-gathering power equivalent to a 5m telescope in diameter, CGST is aimed at becoming a telescope providing the most accurate polarization measurement with the highest spatial resolution in infrared and optical wavelength. The main payload on DSO is a 1m in diameter telescope, targeting at breakthroughs in observing the fine structure of solar magnetic field and so on. On DSO, the key instrument to measure the magnetic field is a two-dimensional real-time spectrograph, which is now under development by HSOS.

  
Two-Dimensional Real-time Spectrograph
Consists of 8-channel birefringent filter. Each channel (i.e., each passband) is equivalent an individual birefringent filter, thus, 8 passbands can construct a rough Stokes profile at same time