Danjon prismatic astrolabe

Danjon prismatic astrolabe

[′dän·yən priz′mad·ik ′as·trə‚lāb]
(engineering)
A type of astrolabe in which a Wollaston prism just inside the focus of the telescope converts converging beams of light into parallel beams, permitting a great increase in accuracy.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.