A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Date: 2014 Dec 6, 07:38 -0000
I think I’ve got it now.
Can’t wait to try this out, albeit at sea level travelling 5 knts, not at 400 feet travelling at over 100 knts!
Well, Chichester did precompute his altitudes but he did it in flight. He did it for pre-selected AP's and times and then the Hps were adjusted for the off schedule time of the actual shot. Loook at the MOB table and you will see that this adjustment is very simple and doesn't require the use of the Bygrave or tables.
From: Francis Upchurch <NoReply_Upchurch@fer3.com>
Sent: Friday, December 5, 2014 3:01 AM
Subject: [NavList] Re: Hughes explanation of Chichester's navigation.
Way to go boys! Wish I could come! Unfortunately grounded, but hope to be well enough for calm water day sailing to Scilly Isles in the spring.
Re: Chichester flight and pre-computed Hps. I bow to your superior knowledge Gary, but I’m a bit confused. In his Astro-Nav war time training book part 4 page 32, he recounts the flight as an example of “running down a position line”. He then clearly states that Alts and Az were pre-computed for expected times and APs to give a mock LOP and the actual LOP drawn parallel to this, separated by the time difference. Hughes, page 54 also mentions that he used the Bygrave to pre-compute Alts and Az to obtain a datum position line through the AP.
Either way, I’ll try your method +/- the Alts/time graph or Moo/mob. And see what I get.
Good flying boys!
Sounds like a plan and a good excuse to put a few hours on your new plane.