NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Index Error - Real vs. Artificial Horizon
From: Bill B
Date: 2013 Feb 28, 16:37 -0500
From: Bill B
Date: 2013 Feb 28, 16:37 -0500
On 2/28/2013 4:32 PM, Paul Fithian wrote: > ------------------------------------------------------------------------ > > While playing around with the sextant, I've noticed a big difference in > index error when viewing things far away vs. near. Paul You are dealing with parallax here (like an old twin lens camera or rifle scope). The path form the horizon mirror and horizon glass are inches apart. That doesn't sound like much until you consider the small angles we are dealing with. For funding index error you want something at least 2 miles away, 4 is much better. Bill B > For example, if I adjust the horizon mirror so that a near (5' away) > horizontal line matches up through the glass and the mirror images, > these images don't line up when I view a horizontal line that is several > hundred feet away. > > Which one do I choose to apply the right index correction for the > artificial horizon readings? I know I have to take the Hs, apply index > correction, then take 1/2 of this reading to get Ho. > ---------------------------------------------------------------- > NavList message boards and member settings: www.fer3.com/NavList > Members may optionally receive posts by email. > To cancel email delivery, send a message to NoMail[at]fer3.com > ---------------------------------------------------------------- > > : http://fer3.com/arc/m2.aspx?i=122540 >