The Collaborative International Dictionary
Nauscopy
Nauscopy \Naus"co*py\, n. [Gr. nay^s ship + -scopy: cf. F. nauscopie.] (Naut.) The power or act of discovering ships or land at considerable distances.
Wiktionary
nauscopy
n. (context obsolete English) The supposed ability to detect incoming ships, before they come into visual range, by studying certain atmospheric effects.