HD 100546 protoplanetary disk dust continuum emission at λ = 0.9 mm. Panels a and b are the images generated using only the SB and LB datasets, respectively, with SB being on asinh scale and saturated to show the faint outer ring. Panel c shows the outer ring structure when the SB and LB datasets are combined after subtraction of the visibilities from the inner disk. The scale bar represents 20 au at the distance of the source, the lower left ellipse represents the beam size of each image, and the numbers to the right of the ellipse indicate thebeam size in milliarcseconds. Panels a and b were generated with a robust parameter of 0.5, and panel c was generated with a robust parameter of 1.8.