Intro.

01jul02: Crosses on J0840+132 to check pointing and gain.

Intro:

01jul02: Crosses on J0840+132 to check pointing and gain.

- Fig 1 top. This is the raw data for a single cross. The units are A/D counts. The blue lines are the fits to each strip.
- Fig 1 bottom. The dome was being moved by maintenance while we were taking this data. The bottom plot shows the dome position as a function of the carriage house position. This motion could change the pointing error.
- Fig 2. The pointing error is plotted versus za (top) and versus azimuth (bottom). The black is the great circle error in the azimuth direction and the red is the error in the zenith angle direction. To figure out the sign convention notice that the azimuth error is always positive. Looking at fig 1 we see that the source is coming after the expected position (it is > 0). If we wanted to point the telescope at the source (with no error) we would add zaComp+zaErr, azComp + azErr/sin(za) to the original encoder values that were used to point at the source. The increase in za error from za=10 to za=15 is probably the dome moving from 19 deg down to 10 degrees (about a 1 arc min variation).
- Fig 3 has the beam width in arcminutes for the lbch. The average is 5.1 arcminutes.
- Fig 4 plots the variation in Tsys versus za (top) and the SEFD bottom for the system. Since SEFD*gain=Tsys a Tsys of 70 K would give a gain of 2 K/Jy.
- Take the recorded az1,za1, ast time from the serial link.
- Compute the model offsets mazoff,mzaoff at az1,za1. The model values are great circle so you need to divide the azimuth offset by sin(za) to go from great circle to azimuth encoder.
- Compute the values prior to the model: az2=az1-maz1, za2=za1-mza1
- Take the great circle errors measured in fig2 above: merraz,merrza and compute the encoder offsets: erraz=merraz/sin(za), errza=merrza.
- compute the theoretical az,za that will be used to go back to ra, dec: az3=az2-erraz, za3=za2-errza.
- Take az3,za3, the time, and the ao lat,long to go back to ra,dec.

To figure out where the seti@home is currently pointing do the following:

home_~phil