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Sunspot Counting: Special Experimental Test Runs

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David W. Rosebrugh

St. Augustine, Florida




In addition to making regular daily sunspot countings as a Standard Observer for the AAVSO Solar Division, the writer has made a series of experimental runs using various types of equipment and techniques. It should be noted that these special test runs have been made upon the writer's own initiative and not under the aegis of the AAVSO Solar Division. The aims of the runs completed so far have been to try to determine the optimum equipment for use in the American Sunspot Counting Program and to try to determine the equipment and procedures required to make countings having a high correlation with those made at Zurich. One test of the projection method, involving 104 daily observations was made. Eight tests of direct observation were made, using refractors equipped with Herschel Wedges and filters. Various powers and apertures were used. These included powers of 29, 45, 60, and 90 and apertures of 60, 76, and 127 millimeters. The F-ratios lay between 12 and 24. A polarizing eyepiece was used in some runs. In one run of 153 daily observations, umbrae with penumbrae were given weightings similar to the procedure followed at Zurich. These special experimental runs started on March 14, 1970 and the latest fully completed study ended on Feb. 29, 1972. Eight experimental runs, direct observation, have been thus far completed. Some of these were run concurrently. These runs involved 815 daily sunspot counts. In these runs counts made with the writer's regularly used 45x76 Cooke refractor were used as "controls". The daily sunspot countings for all test runs have been submitted to the Chairman of the solar Division on a current basis. A statistical report has been prepared for each of the nine completed test runs and copies of these reports, and of future reports, will be placed on file at AAVSO Headquarters. Studies are still continuing, and the tenth test run, comparing countings made in mid-morning with counting made six hours later the same day, was completed observation-wise on April 30, 1972. 116 pairs of countings were made. The statistical report on this run is in preparation. Further test runs are in the planning stage and it is hoped to start these in the fall of 1972.


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