NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: David Pike
Date: 2022 Jun 27, 14:38 -0700
Francois.
You were looking for lost minutes of time of sunrise.
I think I spot two problems.
1. If you start with sunrise is 03.50 local time (which I confirmed in the Air Almanac) at 62° 28’W, you need to add (62x60 + 28)/60x15 = 3748/900 = 4.164 hrs = 4hrs 10 minutes, not 4hrs, to get sunrise at Greenwich i.e 08.00UTC, not 0750UTC
2. From 07.50 to 08.13 is 23 minutes of time.
Interpolating directly, Sunrise at 48° 17.5’N should be 1° 42.5’/5° x23 minutes of time after sunrise at 50N. I.e., or 102.5'/300' x 23 = 8minutes of time after sunrise at 50N, not 18 minutes as you’ve calculated. Overall sunrise at your position should be 08.00UTC + 8 minutes = 08.08UTC. which is a bit closer to Al’s value.
Without knowing more about Al’s spreadsheet and almanac sunrise time, I can’t explain the remaining missing 6 minutes. DaveP
