Maximum reliable distance to which we trace dust, based on our estimate of the distance at which we run out of main-sequence stars in each sightline. The sharp boundaries that run ∼10–25° above and below the Galactic plane correspond to the boundaries at which we switch the angular scale of our sightlines. We generally trace dust to greater distances near the Galactic midplane, where the stellar number density is larger, except in regions where dense clouds block background stars. The arc of increased maximum distance at b ≲ − 45° in the outer Galaxy corresponds to the Sagittarius stream.