διόπτρα

A. optical instrument for measuring angles, altitudes, etc., Euc. Phaen. p.10M., Plb. 10.46.1, Attal. ap. Hipparch. 1.10.24, Gem. 1.4, Ptol. Alm. 5.14, etc.; ἡ τῶν δ. θεωρία Gem. 5.11.

2. aperturesight in a torsion-engine, Ph. Bel. 64.9, 76.48.

II. plate of talc for glazing windows, Str. 12.2.10.

III. = διαστολεύς, Aët. 16.89, Paul.Aeg. 6.73.

IV. σημεῖον ἐν θυτικῇ, Hsch.