At a perihelic opposition , however , Hygiea can reach +9.1 and may just be resolvable with 10x50 binoculars , unlike the fifth and sixth biggest asteroids 704 Interamnia and 511 Davida which are always beyond binocular visibility . At a perihelic opposition , however , Hygiea can reach +9.1 and may just be resolvable with 10x50 binoculars , unlike the next two largest asteroids in the main belt , 704 Interamnia and 511 Davida , which are always beyond binocular visibility .