diplantidian

† diplanˈtidian, a. Obs.

[f. Gr. διπλό-ος double + ἀντί against, opposite + εἶδος form, image + -ian.]

Applied to a form of telescope proposed by Jeaurat in 1778, giving two images, one direct and the other reversed, the coincidence of which might be used to determine transits.

T. Young Lect. Nat. Phil. & Mech. Arts II. 351.