A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2011 May 11, 01:52 -0700
|Mystery still not solved.|
A few observations. Certainly most of the handwriting is Noonan's but the notation about the ship President Harrison is not his hand.
I suspect that some of the labels may have been added after the flight allowing for the wrong name of the star to sneak in. A good example of this is the notation for the Alphecca line that says "ADV" showing the Alphecca line advanced to 0446 Z to cross with the Polaris line to form the 0446 Z fix. There would be no reason for the navigator to make that notation unless, after the flight, he was explaining the chart work to someone.
I still wonder if the actual plotting wasn't done by Harry Manning and Noonan just wrote in the labels at a later time. I base this on the arrows showing the azimuths and these arrows do not appear on Noonan's Atlantic crossing chart. It seems strange that Noonan would change his method of plotting LOPs in just three months. When I plot LOPs I never draw in the azimuth line since I use the "flip-flop" method with an aeronautical plotter. It is possible that Noonan used the method that I use and that Manning used parallel rules.
Thinking about Greg's suggestion I planned to do the calculation for Denebola using H.O. 208 and then see if some easy type of error would produce the 82° erroneous Zn. But on further thought I realized that I didn't have to do this to eliminate Denebola.
I calculated the data for each of the observations. Then by examining the chart it is clear that the intersection of the ZN line with a parallel of latitude is the AP. My calculated GHAs corresponded with the longitudes of these intersections. This provided a way to eliminate potential candidates since the correct star would have to have a GHA with the minutes equal to the measured longitude of the intersection of the Alphecca Zn arrow with the 34° north latitude line. Because the Zn crosses the latitude line at a shallow angle, there is some uncertainty about the correct longitude/GHA value to use. I finally decided that any star that didn't have a GHA in the range of XXX° 17' to 26' could be eliminated. This took out Denebola which had a GHA of 66° 50.9', outside of the acceptable range. This also eliminated Aldebaran, GHA 175° 14.4', also outside of the range.
Keith suggested Alpha Lyncis but that looses out on several counts. First, it is not one of the 57 listed stars in the Nautical Almanac. Giving it some thought, I have never shot any other stars, I have never gone to the back of the Almanac to use one of those other 173 stars, have you guys? The only reason I can see for using one of them is if one the 57 stars were not available. But since you don't use these other stars on a regular basis and, presumably the familiar stars are not visible, how do you know what star you are shooting through that hole in the clouds. On a ship where your DR is much more accurate than in a plane you can take plenty of time and do some calculation to figure out the identity of the mystery star but I can't see doing this in a plane.
A second reason to eliminate this star is that it is not even one of the 173 other stars in the almanac so Noonan couldn't have used it.
A third reason is that its GHA also falls outside of the acceptable range (assuming that its SHA hasn't changed significantly since 1937). Its RA is 09h 21m 03.46
making its SHA 219° 44' which produces a GHA of 103° 03.3', outside the range.
So, the mystery continues.
--- On Tue, 5/10/11, Keith Pickering <firstname.lastname@example.org> wrote: