arcsec
/ˈɑrkˌsɛk/
noun
- A unit of angular measurement equal to one sixtieth of an arcminute, or 1/3600 of a degree. Used especially in astronomy and optics.
- Astronomers measure the apparent size of planets in arcsec.
- The two stars appear only 0.5 arcsec apart in the sky.
- The telescope can resolve details as small as one arcsec.