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Eclipsing Binary Observing ProgramFor more information contact Committee Chairperson Gerry Samolyk (gsamolyk@wi.rr.com).
One of the keys to successful observation of EB stars for the purpose of timing their minima is planning. When one of these stars enters its eclipse phase it will not wait for you to iron out the details you may have overlooked or failed to attend to earlier. A 20 or 30 minute delay to search for a misplaced chart or to locate the star field in an unfamiliar portion of the sky can mean loss of the evening's work. First, the observer must determine what stars he should attempt to observe. His choice of stars should certainly be within the limitations of his instrument and at a declination easily reached from his latitude. Duration of the eclipse may also be a limiting factor. Information about eclipsing binaries, including maximum and minimum brightness, period, eclipse duration, position and other related elements can be found in several publications including the General Catalog of Variable Stars. Charts for eclipsing binaries can be obtained from Gerry Samolyk, 9504 W. Barnard Ave., Greenfield, WI 53228. An ephemeris for AAVSO program stars is available from the AAVSO Headquarters, 25 Birch Street, Cambridge, MA 02138. Armed with a chart, an ephemeris and information about a star's eclipse elements it is always a good idea to locate the star field a few nights in advance of a scheduled minimum. This is a good time to examine all comparison stars to determine which, if any, do not appear to be consistent with the sequence given on the chart. The observer may wish to eliminate any which may seem wrong. If the observer has difficulty coming to terms with his comparison star sequence, probability of success is rapidly diminished. On eclipse night plan to be in place early enough to obtain both the descending and ascending branches of the light curve. As an example, an eclipse with a duration of 5 hours probably should be observed for 3 or 4 hours centered on mid-eclipse. An observation about once every 10 minutes is usually best. All observations should be timed to the nearest minute. So, an accurate time source is essential. A common pitfall for EB observers is observing bias introduced by wishful thinking. Never let your expectations influence the outcome of the observation in progress. The observer may find himself forcing an observation because he thinks it is time for the star to make a move -- or he may force it to maintain a smooth light curve. A forced smooth curve is simply a false curve. Each estimate must be independent of all expectations. Record what the eye sees -- not what you think the eye should be seeing! Data intended for reduction and publication through the AAVSO should be sent to the chairman of the AAVSO Eclipsing Binary Committee. Current procedure permits reports on any standard 8(1/2)" X 11" sheet of paper with any number of stars and minima being reported on one side only. Use the double date notation and specify clearly what type of time is used. Do not convert to Julian Date as all data are entered into the computer as Universal Time to the nearest minute. General correspondence should go on a separate sheet of paper. Only notes directly concerning the observations should be placed on the data sheets. More Information
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