NavList:
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: John Huth
Date: 2009 Oct 11, 07:48 -0400
From: John Huth
Date: 2009 Oct 11, 07:48 -0400
One wrinkle on this for the *stationary* observer is doing measurements when the altitude of the sun is changing rapidly, bracketing noon by a wide margin. The only reason I mention this is that I was surprised how accurate it was.
For my class, I made a rudimentary quadrant, where the angular scale came from successively bisecting angles to get 64 divisions. I'm not claiming great accuracy with this, perhaps 30 arc-minutes at best. I measured the sun's altitude multiple times when it was rising, during meridian passage (for latitude) and then when it was setting. In terms of getting the LAN, the midpoint of the rising curve and the setting curve turned out to be reasonably accurate, given how rudimentary my quadrant was. I got to within 20 arc-minutes of my longitude (which might not sound like anything great to people accustomed to sextants).
Obviously this doesn't work for a moving vessel, but I found it interesting that a crude instrument, coupled with a watch could do a reasonable job in determining longitude.
John Huth
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com
-~----------~----~----~----~------~----~------~--~---
For my class, I made a rudimentary quadrant, where the angular scale came from successively bisecting angles to get 64 divisions. I'm not claiming great accuracy with this, perhaps 30 arc-minutes at best. I measured the sun's altitude multiple times when it was rising, during meridian passage (for latitude) and then when it was setting. In terms of getting the LAN, the midpoint of the rising curve and the setting curve turned out to be reasonably accurate, given how rudimentary my quadrant was. I got to within 20 arc-minutes of my longitude (which might not sound like anything great to people accustomed to sextants).
Obviously this doesn't work for a moving vessel, but I found it interesting that a crude instrument, coupled with a watch could do a reasonable job in determining longitude.
John Huth
--~--~---------~--~----~------------~-------~--~----~
NavList message boards: www.fer3.com/arc
Or post by email to: NavList@fer3.com
To , email NavList+@fer3.com
-~----------~----~----~----~------~----~------~--~---
