An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A rule that gives the direction of the resultant vector in a → vector product: A x B = C. It is the direction of advance of a right-hand screw whose axis, held perpendicular to the plane of A and B, is rotated in the same sense that rotates the first-named vector (A) into the second-named vector B through the smaller angle.

→ right; → hand; → screw; → rule.

Using the right hand with greater skill or ease than the left.

→ right; → hand + -ed.

Râstâl, from râst, → right, + -al→ -al. Râstdast, with dast, → hand.

Atmospheric (→ airglow, → auroral emission, → artificial light) or extraterrestrial (→ scattered  → sunlight from Moon, scattered → starlight, → interplanetary dust) foreground light that → interferes with → observations.

→ sky; → brightness.

The brightness of an extended object, such as a planet, nebula, galaxy, or the sky background, expressed as magnitudes per unit area (usually square arc second). Surface brightness is calculated by dividing the object's magnitude by its size (→ isophotal radius).

→ surface; → brightness.