SFA Radio Interferometry


The fireplot above is from the second half of January 24, 2004 (UT). Time is along the horizontal axis and frequency is along the vertical axis. Note that the vertical strips near the Sun-crossing correspond to interference fringes (see below). This plot shows us that the spectra from the hydrogen in the galaxy is most like an emission spectra with redshifts and blueshifts while the spectra of the Sun is most like a continuous spectra. Note that these data were collected during the rain. The two dishes involved have not been aligned with great care yet. The dishes were set to an approximate declination of -19.

The plot below shows the average voltage over all frequencies versus time for the same data above. The interference fringes (peaks) from the Sun occur about 4.85 minutes (0.00337 days). This corresponds to a 1.213 movement of the Sun across the sky.

Note that nl=d sinq where d is the separation of the dishes.

This leads to a predicted separation of our dishes: d = l/sinq = (21cm)/(sin 1.213) = 9.9 meters = 32 feet.

Michael Johnson's thesis reports that the distance between the SW and SE dishes is 63 meters. Note that the prediction above agrees with new dish-testing locations described below. The true dish-testing locations are not yet available.