Its brightness at these rare near-perihelion oppositions makes Bamberga the brightest C-type asteroid , about one magnitude brighter than 10 Hygiea 's maximum brightness of around +9.1 . Its brightness at these rare near-perihelion oppositions makes Bamberga the brightest C-type asteroid , roughly one magnitude brighter than 10 Hygiea 's maximum brightness of around +9.1 .