GBT response pattern P, as measured from scans of the Sun, on a linear scale. The H and V coordinates are the same as in Figs. 6 and 8. Note that this plot has been rotated so that its features are more easily visible – the vertical coordinate V increases from left to right in this figure. The truncated peak at center-left in this figure comprises both the main beam at (H,V) = (0,0) and the double-peak feature at (H,V) ~ (± 1°, −3°); the peak of the main beam would be far offscale at P = 1.12 × 10⁵. Near the center of the spillover lobe, the Arago spot is visible. The gap at high V in the spillover lobe and its surrounding rings arises from the presence of the reflecting screen at the subreflector edge.