Reticle Plate and Method for Establishment of a North-Oriented or South-Oriented Line by Circumpolar Orientation.

• Main Author: McDonnell,M M
• Other Authors: DEPARTMENT OF THE ARMY WASHINGTON DC
• Format: Text
• Language: English
• Published: 1981
• Subjects: Astronomy; Optical Detection and Detectors; Optics; *Patent applications; *Optical instruments; *Reticles; *Plates; *Celestial guidance; *Stars; *Orientation(Direction); Aiming; Circles; Alignment; Antarctic regions; Arctic regions; Theodolites; Artillery; Circumpolar orientation; *Reticle plates; Antarctic; Arctic; South Pole; Antarc*; South pole
• Online Access: http://www.dtic.mil/docs/citations/ADD010859; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADD010859

A reticle plate provided with a reticle and three concentric circles of varying diameter and methods of use thereof, the invention allows a user to establish a north-oriented or south-oriented line by alignment of selected circumpolar stars with the circles. The circles are located on the reticle plate in positions determined by angles which exist between the celestial north (or south) pole and the particular low-magnitude circum-polar stars chosen as sighting points, the radii of the circles being directly proportional to the objective lens focal length of the theodolite or optical instrument within which the plate is used. A first method of the invention allows ambiguous location of the north or south pole by alignment of each of three selected stars with one each of the three circles. A second method provides data to a user sufficient to locate the pole by alignment of innermost and outermost circles respectively with one each of two of the selected stars.