Arcsecond
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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, directly from the definition, 1 astronomical unit at 1 parsec .
Correspondingly, 1 radian ≈ 206,265 arcseconds.
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.
It can be abbreviated as arcsec, but should then not be confused with the inverse trigonometric function arc secant, which has the same abbreviation.cs:Vteřina da:Buesekund de:Bogensekunde es:Segundo de arco nl:Boogseconde fi:Kulmasekunti zh:角秒