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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sudden shift in sextant sights
From: Bill B
Date: 2012 Mar 28, 21:10 -0400
From: Bill B
Date: 2012 Mar 28, 21:10 -0400
On 3/28/2012 3:34 PM, Zvi wrote: > I went down today to Brighton Marina to take some pre-computed sights. > Basically I pre-compute sun altitudes for a known GPS position just > outside the marina for every 20 minutes, and also note the change in > altitude per minute for each pre-computation (for example – at 11:20 > UTC, calculated altitude for that position was 41 29.0 and it was > increasing by 2.4’ per minute at that time). I then sit on the beach and > take 3 sights every 20 minutes as close as possible to the target time, > correct them according to their time difference from the target time > with a table I prepared, and compare them to the pre-computed calculated > altitude for that time (for example, I took a sight at 14:18:38 which > was 41 25.0 and added to it 3.3’ to ‘bring’ it to 11:20, obtaining an > intercept of 0.7’ away). Large snip For a refreshing change, I'll agree with Alex.... Were it me, I would use an online calculator to reduce each observation and compare that Hc to my pre-computed numbers. Bill B
