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*** Before compiling: change the path to alfa_offsets.tcl in alfaoff.c to point to where the file is on your machine. Fixbeampos fixes coordinates in the main header of Mock psrfits files taken with ALFA up to 28 Jan. 2010. Up to that date, coordinates in the headers and rows of side beam (beams 1-6) data files were not calculated correctly by the Mock data-writing software. Data files from beam 0 are fine. Data with HDRVER of 3.43 or greater in the main header are not affected. The program needs a beam 0 file--it will use the positions in its header and rows to calculate the correct positions of the side beams' headers and rows, and will correct the side beam files if they are present in the current directory. HDRVER in the main header of side beam files will be changed to 3.43. A new field FIXDATE will be added to the main header of side beam files to record the date on which they were corrected. Fields fixed in main header: HDRVER, RA, DEC, STT_CRD1, STT_CRD2, STP_CRD1, STP_CRD2 (the latter two pairs of parameters are "start coordinates" and "stop coordinates", which are equal to RA,DEC) Fields fixed in rows: RA_SUB, DEC_SUB, TEL_AZ, TEL_ZEN, GLON_SUB, GLAT_SUB The calculated RA, DEC, GL & GB for side beams based on beam 0 values are within a few arcsec of actual positions (from tests on data where both header and rows positions were correct for all beams). The calculated AZ may be up to 1.5 arcmin from actual positions, but that is a "small circle" angular distance and may be very large at small ZA. The "great circle" angular offset is AZ*sin(ZA), which is just a few arcsec.