prime vertical

British  

noun

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

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Example Sentences

If your A.M. sight was taken when the sun was on or near the prime vertical, a change in latitude at noon will make no change in longitude.

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.

The usual observations made by navigators at sea consist in a meridian observation of the sun for latitude, and a morning and possibly afternoon observation of the sun near the prime vertical for longitude.

From International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884. Protocols of the Proceedings by Various

The prime vertical circle passes through the east and west points of the horizon.

From Recreations in Astronomy With Directions for Practical Experiments and Telescopic Work by Warren, Henry White

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