Equatorial mount

Abstract: The Xinglong 2.16-m reflector is the first 2-m class astronomical telescope in China. It was jointly designed and built by the Nanjing Astronomical Instruments Factory (NAIF), Beijing Astronomical Observatory (now National Astronomical Observatories, Chinese Academy of Sciences, NAOC), and Institute of Automation, Chinese Academy of Sciences in 1989. It is a Ritchey-Chretien (R-C) reflector on an English equatorial mount and the effective aperture is 2.16 m. It had been the largest optical telescope in China for ~18 years until the Guoshoujing Telescope (also called Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST) and the Lijiang 2.4-m telescope were built. At present, there are three main instruments on the Cassegrain focus available: the Beijing Faint Object Spectrograph and Camera (BFOSC) for direct imaging and low-resolution (R ~ 500–2000) spectroscopy, the spectrograph made by Optomechanics Research Inc. (OMR) for low-resolution spectroscopy (the spectral resolutions are similar to those of BFOSC) and the fiber-fed High Resolution Spectrograph (HRS; R ~ 30,000–65,000). The telescope is widely open to astronomers all over China as well as international astronomical observers. Each year there are more than 40 ongoing observing projects, including 6–8 key projects. Recently, some new techniques and instruments (e.g., astro-frequency comb calibration system, polarimeter, and adaptive optics) have been or will be tested on the telescope to extend its observing abilities.

Abstract: Over the past decade, time-domain astronomy in optical bands has developed rapidly with the operations of some wide-field survey facilities. However, most of these surveys are conducted with only a single band, and simultaneous color information is usually unavailable for the objects monitored during the survey. Here we present introductions to the system of Tsinghua University-Ma Huateng Telescopes for Survey (TMTS), which consists of an array of four optical telescopes installed on a single equatorial mount. Such a system is designed to get multiband photometry simultaneously for stars and transients discovered during the survey. The optics of each telescope is a modified Hamilton-Newtonian system, covering the wavelengths from 400 to 900 nm, with a field of view (FoV) of about 4.5 deg2 and a plate scale of 1.″86 pixel−1 when combining with a 4K × 4K QHY4040 CMOS detector. The TMTS system can have a FoV of about 9 deg2 when monitoring the sky with two bands (i.e., SDSS g and r filters) at the same time, and a maximum FoV of ∼18 deg2 when four telescopes monitor different sky areas in monochromatic filter mode. For an exposure time of 60 s, the average 3σ detection limit of the TMTS system can reach at ∼19.4 mag in Luminous filter and at ∼18.7 mag in SDSS r filter. The preliminary discovery obtained during the first few months’ survey is briefly discussed. As this telescope array is located at the Xinglong Observatory of NAOC, it can have an excellent synergy with the spectroscopic survey by the LAMOST (with a FoV of about 20 deg2) at the same site, which will benefit the studies of stellar and binary physics besides the transient sciences.

Abstract: An equatorial mount for supporting a binocular reflecting telescope having two Cassegrain or Schmidt-Cassegrain reflecting mirror units having the same aperture and the same focal length. The equatorial mount includes a pedestal, a polar shaft (first shaft) supported obliquely by the pedestal. A second shaft is rotatably supported in a support barrel coupled to the polar shaft. A third shaft is rotatably supported in a second support barrel provided at the bottom end of the first support barrel. Counterweights are screwed onto a threaded rod so as to extend from the free end of a V-shaped crank which is mounted on the free end of the second shaft. Another counterweight is screwed onto another threaded rod mounted inside of the crank and extends in the same direction as the crank. The equatorial mount has a greater degree of freedom of rotation compared with a German-style equatorial mount, because it has the third shaft.