NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Polaris for Latitude- why so accurate?
From: Bill B
Date: 2014 Sep 27, 15:36 -0400
From: Bill B
Date: 2014 Sep 27, 15:36 -0400
On 9/27/2014 2:41 PM, Greg Rudzinski wrote: > Polaris changes altitude very slowly just like the Sun at or near LAN. Sam Currently the declination of Polaris is 89°18.5'N. That means it is nominally 41.5' from the north pole. For most of the northern hemisphere it is circumpolar, meaning it never dips below the horizon. If you could view Polaris all day, twice a (sidereal) day it's Hc would be exactly 89°18.5'N. Once a day 89°18.5' minus 41.5', and once a day 89°18.5' plus 41.5'. Azimuth wise, true north twice a day, and off to the east or west the remainder of the day. As Greg pointed out, that is a relatively slow rate of change. While it is great you are absorbing Bowditch, there is a table in the back of the NA (pages 274-276) that adjusts for the change in altitude and azimuth based on LHA Aries, month and latitude. No sight reduction required. The NA, one-stop shopping ;-)
