Astronomers at the United States Naval Observatory (USNO) maintain a list of all the visible measurements, published in the literature, of binary stars. They make available on the world wide web a summary list (http://ad.usno.navy.mil/ad/wds/wds.html. Also at the USNO web address are lists of single stars, and multiple star systems with orbital elements. By observing single stars, one can test new data reduction techniques. Systems with known orbital elements are useful for determining the exact scale and orientation of the optical system on the sky.
The above mentioned summary list makes a good starting point for a project of study. For the data to be useful, it is necessary to calibrate the data accurately. The best way to do this is to look at known, slow moving systems - a system that has not changed position angle and separation significant for the last 200 years is a good candidate for scale and orientation calibration. It is necessary to observe several of these systems before taking apart or modifying the optical system.
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