NavList:

Mr.F.Reed . The text concerns the Earhart-Noonan flight of July 2 , 1937 , first leg , from Lae to Nukumanu . On the rhumb line Gagan on Buka to Nukumanu locates the coordinates pair 159-07´-E ; 04-33´.5-S . These figures appear in the from aboard the aircraft 0718 GMT radio message . Sunset over this position was @ 0719:30 GMT . Re-computation by H.O.no.9 -II for the rhumb line places the sunset position of aircraft exactly on the Gagan-Nukumanu loxo , and any computation , be it by direct spherics , H.O.no.208 , or p.e. the Douwes-Borda formula gives the same time-coordinates-sunset group , indicating that mr.Noonan actually precomputed this sunset fix .

Evidently ,to avoid adverse weather @ 250-300 mls off Lae as from the last received forecast , the aircraft was first steered to Ghaghara on Choiseul Island in 157-E ; 07-03´-S (0519 GMT radio). At 0718 GMT however , Earhart reported to be over the originally precomputed sunset on-board position 159-07´-E ; 04-33´.5-S .
From Ghaghara to this sunset location the distance is 226 (land) miles and the point is 27 miles west of Nukumanu . Thence , because of the optical intricacies of observing actual sunset , it is a reasonable assumption that Noonan ordered the aircraft to DR steer from Ghaghara to the sunset coordinates by drawing the loxodromic course in the chart , observe superficially for sunset (unarmed eye , bubble sextant , or pelorus for azimuth) against 0719:30 GMT , and communicate the "Fix" having been reached , by which the aircraft was back on its intended track to Nukumanu .
Consequently , the analysis is not from thin air , although no verification can for the era be found , specifically for air navigation purposes in literature ,than in Dutton , Navigation and Nautical Astronomy , 1928 Edition , p. 311 , art. 348 . The paragraph was deleted for editions after 1934 . Noonan was , before 1934 , a professional sea navigator and he must have known the sunset-sunrise fix fashion , like , btw , any other sea navigator of the era.

Aircraft´s altitude @ sunset was 7,000 feet , no visible horizon , observation by the bubble sextant was an option if superficial observation was considered too erratic .

As an emergency operation , the sunset-sunrise fix also appears in , e.g. , Navigators Information Files of WW-II , with correction for aircraft´s altitude (NIF Oct 1944 , Section 3 , § 7-2)

The Neherlands Wikipedia contains the article you mention . The text is not from my hand , although I contributed to the "discussion" page (where I can not find back my remarks now). The article is not updated (like the ones on Earhart/Noonan in the English Wiki). I suppose the published text was taken from my remarks , as far as contemporary knowledge reached ; my first article (of 3) on the subject in European Journal of Navigation is of July , 2008 . The specific Sunset Fix re-computation (by H.O.no.208) is shown in the article of April , 2011 .

HvA
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