Square degree

Square degrees (deg ², (°) ² ) (English square degree or sq. degree) is an obsolete, non-legal (since 1 January 1978) unit for the solid angle. Application finds especially in astronomy as a measure of the extent of an object in the sky. The subunits are called according to square arc- minutes (English square arcmin, 1/3600 square degrees ) or square arc- second ( English square arcsec, 1/3600 square minutes).

The full solid angle of the celestial sphere is 360 ² / π ( approximately 41253 ) square degrees, according to 4π sr. The size of a celestial object in square degrees is thus obtained from the fraction of the celestial sphere, the object covered multiplied by 41253rd For small angles with solid angles can be approximated as expected surfaces. An object whose expansion measures in a direction perpendicular to 1 degree and also 1 degree, therefore, covered a solid angle of about 1 square degree. Applies to conversion

Opening angle of 0-45 °.