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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Artificial Horizon
From: Richard M Pisko
Date: 2011 Jul 24, 20:16 -0600
From: Richard M Pisko
Date: 2011 Jul 24, 20:16 -0600
On Wed, 13 Jul 2011 06:08:37 -0600, G Beckerwrote: > The plane table is a lost art, what are you mapping? How are you > transferring the north information from the sextant to the location of > the table? I did not see an answer to your question, possibly because it was a private communication or possibly my server did not pick it up. At any rate, my best guess for the use of a sextant would be for determining differences of elevation between objects of known distance, although an Abney level would be more convenient. For traditionalists, the Indian pattern Clinometer has an angle scale and a tangent scale. More accuracy, both in reading the vertical angles and in sighting the objects, may be had from various telescopic alidades, most of which will have tangent scales or Beaman stadia arc scales in addition to the vertical angle and accompanying vernier scales. The table may be roughly oriented by a compass and a line on the sheet pointing to magnetic north (allowing for magnetic variation), and more accurately by a Solar compass sheet, knowledge of Latitude and Longitude, and an accurate watch; but the table is most easily oriented by trial and error as a three point resection problem (if suitable known points are already plotted on the sheet). -- Richard . . . Using Opera since the"Dog" died