Arcsecond

A second of arc or arcsecond is a unit of angular measurement which comprises one-sixtieth of an arcminute, or 1/3600 of a degree of arc or 1/1296000 ≈ 7.7?10-7 of a circle. It is the angular diameter of an object of 1 unit diameter at a distance of 360?60?60/(2π) ≈ 206,265 units, such as (approximately) 1 cm at 2.1 km, or 1 astronomical unit at 1 parsec, which is the definition the parsec.

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Correspondingly, 1 radian ≈ 206,265 arcseconds.

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The symbol for marking the arcsecond is the double prime (″) (U+2033, ″). One arcsecond would be 1″ (or 1"). The double prime symbol is also used to denote the inch: this can, in certain contexts, cause confusion.

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It can be abbreviated as arcsec, but should then not be confused with the inverse trigonometric function arc secant, which has the same abbreviation.

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Angular: The angular is a large bone in the lower jaw of amphibians, birds and reptiles, which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the articular....

Arcminute: redirect minute of arc...

Degree of arc: REDIRECT degree (angle)...