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

The fact of being in line or bringing into line.

Verbal noun of → align; → -ment.

→ Deviation of the chain of → optical components from the optimum → alignment in an instrument which leads to → loss of → light and poor → image.

→ mis-; → alignment.

The process or the state of making a → telescope's → polar axis → parallel to the → Earth's → rotation axis, that is with the → true North or → South  → celestial pole. When this is accomplished, the sky's motion can be cancelled out simply by turning the axis (either by hand or with a motor → drive) at the same rate as the rotation of the Earth, but in the opposite direction.

→ polar; → alignment.