swinging the arc
swinging the arc[′swiŋ·iŋthə ′ärk]
The process of rotating a sextant about the line of sight to the horizon to determine the foot of the vertical circle through a body being observed. Also known as rocking the sextant.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.