Data Reduction

On-The-Fly mapping produces enormous amounts of CLASS data even at the current slow dump rates. With all 6 backends connected, about 27 kB of data is written every 2 seconds. It is therefore recommended to keep the size of the SPECTRA.SMT file small (less than 20 MB or a few thousand spectra) since the VAX's data reading and writing efficiency drops very fast for large files.

The spectra's offset positions are derived from the backend time stamps and represent the actual telescope position at the time of data taking. The positions are calculated for the center of the dump and do NOT have to be corrected for zig-zagging.