Since this is my first post I'll say hello all a give a tidbit of my background!
I've been interested in AE's fate and reading this site for about 13 years.
I've also read Elgin Long's book, and am familiar with almost every site on the subject.
You may laugh, but I've been flying the FS Simulators since FS2000 version.
In the last couple of years several friends and myself have worked to develope a good model of Amelia's Lockheed L10E.
It is equipped with a sextant,driftmeter, E6B, and includes different gauge failures built to at random.
http://www.flightsim.com/vbfs/forumdisplay.php?10-MSFS-Multiplayer-AdventuresOne of the persons who has developed this program has done extensive research on AE in several different locations including the Smithsonian and corresponded with Elgin Long, as well.
I'm also familiar with the Purdue University's Archives on Amelia Earhart the Putnam collection.
I'm also a real world pilot and have been a Ham Radio Operator for years, so I know a bit about propagation, directional attennas, signal strengths, and mores code, which IMHO believe Amelia Earhart should have know as well.
All these things have led me to my own theories, but this post isn't about my opinion but is here for its factual value.
I found researching this particular subject interesting and find it hard to believe anyone is inquiring as to whether or not FN used the MOON to navigate!
Of course he use the MOON as his primary LOP and this post will prove to you WHY he used it!
Some sources, and I’m not pointing fingers, have suggested that FN was confused and was reading the wrong dated charts and instead of using Jul 3 data he may have been using Jul 2 data or vice versa. In fact one person goes into a very long dissertation, which is almost convincing, until you realize he fails to mention one very important detail, which would have been quite obvious with the use of the naked eye alone. (the MOON was available that night) The argument has also been supposedly confirmed by some navigator and that these chart errors could have put them 59.14 nm farther east or west of where they actually were.
I say nonsense! Here is a comparison of those two days of readings.
As example, if that were the case then the errors would have been as follows just before crossing the IDL (International Dateline)
For anyone who knows nothing or very little about celestial navigation here’s a crash course or refresher perhaps for navigators.
Fact: Fred N would have definitely taken three shots to acquire three LOP’s each time he was acquiring a fix at night. We know that from his Oakland to Hawaii records and that was protocol in those days.
You may ask why?
Take a piece of paper and draw a big X on it. Call where the lines intersect a two LOP fix. To confirm this fix the navigator takes another LOP and draws the third line on his graph. The third line should intersect exactly where the first two did. If not he knows exactly which one of the three LOPs is incorrect. And since the MOON would be the one so far off if he were reading the wrong day’s charts, he’d know it immediately. So he’d use at the next day’s chart, depending which side of the two star fix was, and recalculate.
Celestial Navigation Data for 1937 Jul 3 at 17:00:00 UT
Latitude S0* 06.1’ Longitude E 179* 56.1’
Object/GHA/Dec/Hc/ Zn
VENUS/ 122* 03.9'/ N16* 10.8'/ +30* 33.6'/ 71.1*
ACHERNAR 152* 27.1'/ S57* 32.9'/ +28* 29.2'/ 163.6*
MOON 139* 54.0'/ N17* 37.4'/ +46* 42.1'/ 63.7*
And readings from 1 day's charts at the some time and place.
Celestial Navigation Data for 1937 Jul 2 at 17:00:00 UT
Latitude S0* 06.1’ Longitude E 179* 56.1’
Object/ GHA/ Dec/ Hc/ Zn
VENUS/ 122* 04.8'/ N15* 56.4'/ +30* 37.0'/ 71.3*
ACHERNAR/ 151* 27.9'/ S57* 32.9'/ +28* 12.2'/ 163.1*
MOON 153* 09.0'/ N13* 34.9'/ +60* 02.1'/ 61.8*
The above star coordinates( VENUS and the MOON are the longitude (east and west) LOPs since their azimuths fall more vertically on the chart or, map if you’d rather think of it as such).
The difference in elevation of VENUS Hc is 3.4 minutes and Dec is 4.6 minutes.
The difference in elevation of ACHERNARs’ Hc is 17 minutes and Dec is 0 minutes (none).
(ACHERNAR is used to determine a latitude (north and south) LOP since its azimuth falls more horizontally on the chart or map).
Sometimes pictures help make things clearer
Draw a typical 30/60/90 degree (right triangle) and label it.
Label the 30 degree angle X to be the Hc (elevation angle) of the star, Side A is the side opposite of Angle A and represents the elevation of the star above the horizon, side B is the adjacent side (111nm) of angle A, and C is the hypotenuse. Use 28 degrees for Angle X.
In case you're wondering why 111nm, it is AE's average GS from the Lae Airstrip to when they reported being 200nm from Howland at 17:42 UT.
By using simple trigonometry (
http://www.pagetutor.com/trigcalc/trig.html) as navigators do, for side B use 111, representing the distance traveled in an hour, and calculate. Increase or decrease angle X by 1 degree and leave side A's value and recalculate. Notice that only a difference of 5nm. Now divide 17 (minutes) by 60 (minutes) = .2833x5nm=1.4nm error.
Since each minute of latitude = 1nm and longitude (at or near the equator) is very close to 1nm, we can see that, if FN had used the wrong dated charts, the error differences in his star LOPs to acquire a fix, would only have been at most about a couple of miles.
(The bubble sextant is only capable of reading within about 4-5nm while bouncing alone in an aircraft like the L10E). So you can see, the difference is quite negligible.
Which is the first point of this exercise of using the wrong day's data charts.
HOWEVER!! Since FN used the MOON as a 3rd LOP using the same method above notice a huge difference!
The MOON would surely be his primary celestial candidate, because of its brightness, accuracy of shooting a LOP with the sextant, and the simple fact that it’s changing its position faster than any another celestial bodies in the sky, including the Sun or planets.
Notice above, that by using the Moons’ LOP as a third source to acquire a fix, the difference in Hc’s are 14* 40’ and Dec’s 14* 14’ from one day to the next. Again, by using simple trigonometry, 111nm as Side B and an Hc of 46 for angle X and increase angle X by 14 degrees to 60. leave side A and recalculate and to see that side B decreases to a reading of 66nm, a difference of 45nm.
Do the same and calculation and decrease the 46 by 14 = 32 and notice the error increases to 184 a difference of 73nm.
Note: Since the Dec and Hc have both changed by around 14 degrees, to be more accurate. you would merely use Pathagora’s Theorem a2 +b2 = c2. The difference in error between the two days would be a little more than 14 degrees. In this case I merely use 14 degrees which is close enough for illustration purposes.
Also note that the errors increase as take reading closer to the horizon which increases accuracy of readings of course.
So supposing FN was using the wrong chart and plotted two star LOPs to acquire a fix (where the two LOP lines intersect) and then acquired the MOON’s LOP. That line wouldn’t even come anywhere near to where the two star LOPs crossed to indicate a fix even if he was just one day off.
There's no doubt that FN would have used the MOON as a third shot since, as a trained navigator for many years, he knew this. If he was using the wrong day’s data he would have known immediately. Not after the crossing the date line and comparing two day's data. He would have known it by merely glancing at the charts and noticing the disparity. Anyone who has looked at the MOON on two different nights knows how much higher or lower it is from one day to the next.
We all know that AE and FN left Lae, NG for Howland island on the 3rd of July, local time.
However FS used July 2nd Charts to whole way since the charts based on GMT not locat time.
It made little difference to Fred when or where they crossed the ILD (International Date Line)
He only cared that he was changing from using a +179 degrees to a -179 degree for reference purposes.
I hope this helps all to understand a little more about Celestial Navigation, the Sextant, and the myth about using incorrect charts.
Fred