Why so much concern over whether AE saw a ship or just 'lights'?
It affects reconstruction of the path of the flight in the middle of night.
How far from land would Ontario or Myrtle Bank have been when the spotting would have occurred?
I have attached another chart showing two options for flying from the position reported in the 0718 Z radio transmission to Howland. Flying directly to Howland is 1,716 SM while over flying Nauru to Howland is 1,746 SM,
only 30 SM longer, about 12 minutes more flying time, about eight gallons of gas. If Noonan had already been giving thought to a landfall approach to Howland, with the interception to take place northwest of Howland, then flying over Nauru would be even less out of the way since it would be more
ON the way to the interception point. In this case it would only be
10 SM longer, 4 minutes flying time and about 2 gallons of gas.
As I posted before, people are too wedded to the line drawn on the chart connecting Lae to Howland and put way too much emphasis on trying to stay exactly on that line than it deserves. I have shown mathematically that there is very little penalty in deviating even great distances from the direct line and, if the deviation allows you to pick up even a slight tailwind, may actually result in a shorter flight time and less fuel consumed. I have also posted that the two charts we have that were actually used by Noonan on the Earhart flight, one from Oakland to Hawaii and the second from Natal to Dakar, show that Noonan didn't come anywhere close to staying on the preplanned direct line. In spite of this evidence to the contrary, people still are in love with that straight line from Lae to Howland. However, we don't have Noonan's chart for this flight (he took it with him) so we don't know exactly what lines
HE drew on
HIS chart for this flight. All we have is a planning strip chart
NOT drawn by Noonan but drawn by Clarence Williams many months earlier when the planned route was in the opposite direction. The navigation FROM Howland TO Lae was a much different navigational proposition because the target was located on a large land mass itself and, even before arriving at New Guinea, they had the island of New Britain on their right side and they also had to cross the entire chain of the Solomon Islands that stretches a thousand miles across their course line, very hard to miss that, it was like aiming at a continent. It would be a much easier task finding all that land and then following it to Lae. With all this land to aim at Earhart didn't even really need a navigator since dead reckoning would have been entirely sufficient for that route. (I have attached a second chart showing this situation.)
Going from Lae to Howland required finding a very small island at the end of a long over water leg, a much more difficult navigational task. Noonan could then be forgiven, after looking at William's strip chart, if he decided on a different route than Williams had chosen. Plus Noonan had a
new piece of information that Williams didn't have (and would have meant nothing to Willilams even if he did) that Nauru had extremely powerful lights (think of stadium lights) used for working the guano mines all night. Noonan knew that Ontario was
supposed to be on station but there would have been some uncertainty about its effectiveness, it could have had a problem, run out of fuel, or been off station at the time that Noonan would be flying over the ship. If Noonan wanted to use it as a check on his navigation up to that point then there would be uncertainty in the derived position because the ship might not be exactly on the assigned station. Earhart had also been informed that Ontario did not have radio capability to hear her transmissions or to communicate with her directly. In order for Ontario to start transmitting a homing signal it needed to be informed that Earhart was on the way and Noonan knew that he would have to trust others, not under his control, to get that message to Ontario and he also knew that he would not have any confirmation that the message had been delivered to Ontario, he would just have to cross his fingers. But looking at the new information about Nauru he knew that the island would be exactly in the same place where it was supposed to be and the lights of the Ontario, no matter how powerful, could never compete with the lights of Nauru. He could feel much more certain about spotting those lights, and from a greater distance, than he could feel about spotting the Ontario.
And they were not mutually exclusive choices. If he started receiving the radio beacon from Ontario then he could change his plans and head for Ontario, if not, then he still had the certainty of finding Nauru. After overheading Ontario he could still fly over Nauru for a precise navigation check if he felt he needed it.
So taking all of this into account, spending eight gallons and only 12 minutes to provide extra certainty in the navigation would be a good choice to make and Noonan was a good navigator.
gl