For a few months I have been monitoring the system temperature of the telescope using data obtained from drift scans of the Sun taken at noon each day.

I thought it curious that there was so much variation in system temperature though basically the Tsys data does follows the Solar Flux Unit data which is obtained from "Solar Radio Monitoring Programme"* of the Canadian Space Agency which, incidentally, is where I obtained the algorithms.for converting their data collected at 10.7cm to the 21cm values needed by my telescopes receiver.

The Sun, having an angular diameter of approximately half of one angular degree, is quite small compared to the 4 degree beamwidth of the telescope at 21cm, so the backgroung temperature is quite significant.

I have been using a background temperature value of 3.5 degrees K as this is what has been suggested would be suitable for a small diameter telescope, but it would appear that an estimation of the background temperature for each data set would be advantageous. Since the beginning of this month, June, the Sun has been approaching the Galactic plane towards the anticentre and the background temperature has therefore been rising quite significantly and it would be interesting if a peak in Tsys coincided with the transit of the Galactic plane on the 21st of this month.

I shall be monitoring and updating this on a regular basis for the next few weeks.

References.

*ftp://lynx.drao.nrc.ca/pub/solar/FLUX_DATA/fluxtablerolling.text