The 50 centimeter Binocular Network (which was referred to as "mini-SONG" during previous SONG workshops) is a Chinese initiative to maximize the scientific potential of SONG's infrastructure. It was proposed when China joined the collaboration. 

50cm Binocular Network (50BiN) project:


tiny logoThe 50BiN project is a Chinese initiative to perform studies of stellar variability, which has baan planned as a sub-system within SONG. The global site plan is exactly the same as the locations of the SONG telescopes in the northern hemisphere: i.e. in the Canary islands (Observatorio del Teide), West-China (PMO at Delingha), US continent (APO) and Hawaii islands (Mauna Lua). Other additional sites, such as the 50cm telescope on the Virgin islands (Etelman Observatory, UVI) after an instrument upgrade, could also join the network to ensure better coverage. Pioneering large field time domain studies of stars by MACHO and OGLE showed that nearly all stars oscillate at various frequencies and amplitudes. Red giants usually show complicated oscillating properties as shown by very extended observations of stars in Galactic bulge. Previous observations in time series for open clusters discovered many different types of variable objects such as intrinsic oscillators, outbursts and transiting types. However, discoveries like this are usually limited by the durations of the observation windows and therefore can hardly lead to meaningful statistics. With traditional single-site sampling, detailed analyses of the oscillation properties of pulsators (usually in multiple modes), the detection of transits and outbursts (with various eclipsing periods or frequencies), and observations of many other interesting phenomena are not always able to reach a high enough completeness level to allow for good statistics in star clusters.  Stars in clusters, which have a near-uniform set of physical properties, can provide much more information for the study of both individual stars and for statistical studies than field objects are able to do. The ability of 50BiN to achieve a long time baseline, combined with a high duty cycle and fine cadence photometry in dense open clusters should make it a powerful tool to enable and push forward a wide range of stellar research interests. Being a part of SONG, 50BiN will have great potential in time-domain astronomy thanks to SONG's infrastructure platform. Apart from targeting a number of carefully-selected open clusters, 50BiN will also be used to perform many target-of-opportinity observations and other special studies that require, or would benefit from, such a network.


Fundamental Requirements for hardware:

  1. To achieve the required long time base line and high duty cycle, a 50BiN telescope should be attached to each SONG node, at least in SONG-North;
  2. To realize our science goals, a (simultaneous) 2 color (UBVRI or SDSS filters) photometry system is necessary;
  3. To cover a large enough area in clusters and around their vicinities, especially for the well-studied old populations of clusters such as M67, NGC188, NGC7789 etc., a minimum FoV of 20'x20' is needed;
  4. We have chosen an aperture of 50cm to optimally match the capabilities of 50BiN to our science goals whilst remaining within our budgetary limits;
  5. To obtain ideal sampling, 2kx2k CCDs are needed;