he·li·om·e·ter 
(hē′lē-ŏmĭ-tər)
(hē′lē-ŏmĭ-tər)n.
A telescope equipped to measure small angular distances between celestial bodies or the angular sizes of celestial bodies.
he′li·o·metric (-ə-mĕtrĭk), he′li·o·metri·cal adj.
he′li·o·metri·cal·ly adv.
he′li·ome·try n.