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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Fix by equal altitude sights around local apparent noon
From: Paul Hirose
Date: 2009 Oct 14, 15:54 -0700
From: Paul Hirose
Date: 2009 Oct 14, 15:54 -0700
A 1915 article in "Popular Astronomy" described the principle and construction of the prismatic astrolabe for observing at a fixed 60° altitude. http://articles.adsabs.harvard.edu/full/1915PA.....23...96B As far as I've heard, the instrument never caught on with the U.S. Coast & Geodetic Survey. They relied on the Bamberg portable transit instrument, which observed in the plane of the meridian in the conventional manner. In the "Monthly Notices of the Royal Astronomical Society", Australian astronomer W.E. Cooke described an equal altitude method for determining latitude and longitude or time by theodolite: http://articles.adsabs.harvard.edu/full/1903MNRAS..63..156C Cooke mentions Chandler's 1887 article on the "almucantar". It's online at the ADS site too: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?journal=AnHar&year=%3f%3f%3f%3f&volume=..17&letter=.&db_key=AST&page_ind=6&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES That peculiar name is what Chandler called his equal altitude instrument, which was different from the prismatic astrolabe. It floated the telescope on mercury! -- --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList+@fer3.com -~----------~----~----~----~------~----~------~--~---
