1.3 mm continuum images of HR 8799 from the SMA (left), ALMA (middle), and the combination of SMA and ALMA (right). These images were obtained with natural weighting, and those including SMA data use a $4\arcsec$ FWHM Gaussian taper to improve surface brightness sensitivity at the expense of angular resolution. The ALMA image is comparable to Figure 1 of @booth16, with a beam size of $\sim1\farcs5$, and it shows a noisy ring of emission surrounding the star. For the SMA image, the beam size is $\sim4\times$ larger in each dimension than for the ALMA image, and the noise level is an order of magnitude higher, but the sensitivity to larger angular scales provided by the shorter baselines enables a much improved representation of the radially extended belt of emission around the star. The combination of SMA and ALMA data results in an even better image of this circumstellar structure. In the SMA and ALMA combined image shown with a $\sim3\farcs8$ beam, the two peaks visible on either side of the star are the signatures of limb brightening along the major axis of an inclined and optically thin emission belt.

Figure \[fig:vis\] shows the deprojected visibility function for the emission from 