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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Precomputing sextant observations at sea
From: Gary LaPook
Date: 2014 Jan 27, 02:10 -0800
From: PharmDoc
To: 'Gary LaPook'
Sent: Sunday, January 26, 2014 7:26 AM
From: Gary LaPook
Date: 2014 Jan 27, 02:10 -0800
----- Forwarded Message -----
From: PharmDoc
To: 'Gary LaPook'
Sent: Sunday, January 26, 2014 7:26 AM
Oh, thank you so much Gary. That is perfect! I did not know about the graph method which looks much better. I realize it is aviation rather than nautical, but still rather magical.
When you say “Before plotting the graph, apply the observation corrections with reversed signs so you actually plot Hp (precomputed) not Hc and then compare your Hs directly with the graph.
Why didn’t Chichester do this? (apart from dip which I guess was different for each obs due to altitude above sea level changes?)
Yes, I chose the 6-7 hour trip to mimic the duration of the Chichester Norfolk- Howe trip. If it works, I’ll try it to cross Irish Sea to Cork 140nm! Last time I cheated with sun/moon fix which is easy! (why didn’t Chichester try to plan his very dangerous flight for a time/date when he could have got a couple of moon /sun fixes?).He would still need to run down the LOP at the end, but a good fix or 2 would have reduced the stress!
If you find time to figure out the question on Chichester’s “square fixes”, that would be great.
Keep up the good work on all this.
Francis
