Continuum Five Point Maps

After the relevant parameters have been typed in and the program has been activated, the following sequence of events takes place:

1. The telescope points at position 1R (see Figure 4.6 or Figure 4.7) and then commences to position switch between 1R and 1M. After completion of the commanded number of on-off's, a continuum SCAN is stored, and the total power measurements are reduced to provide an antenna temperature for the source when measured HP degrees above the assumed source position in elevation. This temperature is printed on the output device given by the RESULTS keyword.
2. The telescope follows the same procedure for position pairs 2R-2M, 3R-3M, 4R-4M, and 5R-5M.
3. According to the keyword FITBW the temperatures computed for each of the five positions are then fed into a least-squares gaussian fitting routine to determine the actual source location relative to position 3. These fitted parameters are displayed on the device assigned by the RESULTS keyword along with estimates of their uncertainty.
4. The telescope then returns to the assumed on-source position, i.e. position 3M.

If you wish SPA can be used to do your own fit of the five point map data, or to fit several maps simultaneously. The five point scans should be simultaneously reduced and put in an S-file (say, S4) using the command sequence
S4 = SCAN # to SCAN # INT
INT will compute the ON-OFF amplitude for each continuum scan plus an estimate of the noise (if more than two repeats were used). Then set the Z variable in PEAK to (YMAX) and perform the Z-D gaussian fit with the command
S4 PEAK
which also prints results of the fit.