NavList:

Gary,

I just did a canned simultaneous time sight of the Sun and Moon then looked up the GHA exactly one hour earlier to figure the time sight longitude. The longitudes differed by 28.3' which was the exact number listed as the ddGHA for the Moon. This ddGHA was from an online almanac not the Nautical Almanac. At Frank-what is this ddGHA number? 28.3' works out to .008' per second of time which means recovering time to better than 30 seconds would be tough.

Greg Rudzinski

[NavList] Re: Recovering Time by Time Sight
From: Gary LaPook
Date: 18 Dec 2012 09:27
We've discussed that method before and it's lesser accuracy but any additional navigational information that you have is useful. I think it is interesting that this method is at the heart of GPS, without it each of our GPS enabled devices would require an expensive atomic clock. The GPS in your phone, wristwatch, etc. has only a relatively inaccurate, cheap, clock and the GPS adjusts the presumed time from that clock to get the LOPs from each satellite to intersect at a point just like adjusting the time to get the moon LOP to cross through the star fix. When it does, you know the time is correct.

gl

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