prime vertical

British

noun

astronomy the great circle passing through the observer's zenith and meeting the horizon due east and west

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

Sun Sight In order to make this a valuable sight for longitude it should be taken when the sun is on or as near as possible to the prime vertical.

From Lectures in Navigation by Draper, Ernest Gallaudet

The sun might be observed for this purpose during the summer months, at moments when calculation showed that he should be due east or west, or crossing what is technically the prime vertical.

From The Contemporary Review, Volume 36, September 1879 by Various

As the sun, in North latitudes, passes the prime vertical before sunrise in the winter, the following remarks do not hold for that season.

From Lectures in Navigation by Draper, Ernest Gallaudet

The amplitude of a star is its distance from the prime vertical, measured on the horizon, north or south.

From Astronomical Lore in Chaucer by Grimm, Florence M.

Take the morning sight for longitude when the sun is on or as near as possible to the prime vertical.

From Lectures in Navigation by Draper, Ernest Gallaudet

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023