A Rapid Computer Search Technique for Astronomical Catalogs

Walter J. Weller
1964 Publications of the Astronomical Society of the Pacific  
During 1963 Hynek and Crull put a modified form of the Yale Catalogue of Bright Stars on punched cards. The writer has used a scan program to convert these cards to a binary tape, i.e., a tape on which the data are in a form immediately usable by the computer. Right ascension (in radians) for instance, is in floating-point format, so that it is available for use without preprocessing as soon as it is read. In addition to obviating preprocessing, the binary format is more compact, allowing
more » ... r records and faster reading. This example of computer search technique is described below. Construction of the binary data tape has involved the following steps: The tape "image" of the punched card is scanned, item by item, and the data are converted to the appropriate binary form. Upon encountering a valid data item, i.e., one which is not blank, the scan program enters a bit into a special computer word called the "missing items" or "data summary" word. A bit in position one of this word means that a valid magnitude is present for the star ; a bit in position two indicates that a spectral type is available. Position seven tells the presence of a trigonometric parallax, and position thirteen a radial velocity. A second word, called the "logic" or "special information" word, is also built during this initial scan. A bit in position one of this word means that the magnitude is variable, in position Editor's note: The use of high-speed computing machines has often been mentioned in these Publications. This paper presents, for the first time, a description of a technique useful for astronomical research, which should be of general interest. Although we occasionally publish short papers on methods, techniques, and instrumentation, our editorial policy of emphasis on the results of astronomical research remains as before. 152
doi:10.1086/128073 fatcat:6o4hzp5gszebrf26sx5sxv7j3y