A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: accuracy of Cook's lunars
From: John Huth
Date: 2013 Jan 10, 16:38 -0500
From: John Huth
Date: 2013 Jan 10, 16:38 -0500
She's a history concentrator, and I walked her through a similar exercise already. She was quite careful, and I'm pretty happy with the result. I'll pass on your e-mail.
On Wed, Jan 9, 2013 at 6:15 PM, <eremenko---.edu> wrote:
I can conclude from this message that your student understands what
she is doing, and that was a serious research.
If she continues her research in this direction
(is not clear from her message whether she intends to), I would like to be
on her mailing list. Please pass her this message and my e-mail:
> On Tue, Jan 8, 2013 at 1:11 AM, Geoffrey Kolbe <geoffreykolbe---com
> Alex (et. al.) -
> Here are some answers from my student regarding her project on Cook's
> I tend to agree with her that a lot of work on this kind of thing is one
> successive approximation. You try to fit the data, the fits raise
> questions, you look at the data in another way, etc etc. (I omit my
> questions, but they're along the lines of what we've discussed).
> Begin clip
> As much as I would like to duck behind bravado, I have to say I'm pretty
> stumped. You've raised many good questions, and I'm not sure I have
> satisfactory answers. But here's a try.
> Most of Cook's coordinates were taken at sea, but he is careful to make
> distinctions. The journals are useful in that they do not merely log data,
> but flesh-out measurements within the context of a narrative. For example,
> Thursday 12/14 (1769): In the evening, having split the shore and mizen
>> topsails, we brought the ship under her courses; and at midnight, we
>> and stood to the southward till five in the morning ... we discovered
>> we had fallen much to the leeward since yesterday morning. At noon, our
>> latitude by observation was 34 degrees 6 minutes south ... and at noon
>> next day we were in latitude 34 degress 10', longitude 185 degrees 45' W
>> and by estimation about seventeen leagues from the land.
> Being a sponsored scientific expedition, Cook and his crew made conscious
> efforts to be precise about their measurements. Most (though not all)
> longitude & latitude sightings were described in relation (or lack
> to land. It's for instance clear that the coordinate readings in the above
> excerpt were not made on land, but in the middle of sea. Others, however,
> were recorded and refined on land:
> Monday 12/11 (1769): Early in the morning, we stood in with the land,
>> leagues to the westward of Doubless Bay, the bottom of which is not far
>> distant from the bottom of another large bay, which the shore ... being
>> separated only by a low neck of land, which juts out into a peninsula
>> I have called Knuckle Point. About the middle of this bay, which we
>> Sandy Bay, is a high mountain, standing upon a distant shore, to which I
>> gave the name of Mount Camel. The latitude here is 34 degrees 51' S and
>> longitude 186 degrees 5'.
> I also read in a secondary source that the majority of lunar readings were
> made by Charles Green, assistant to Astronomer Royal Nevil Maskelyne (the
> lunar guy himself). To be precise, he recorded hundreds of sets of lunar
> observations for locations to be incorporated into new maps. This would
> have been possible in mid-ocean ship conditions (I think?).
> In other words, most of the time, Cook was clear about location:
> observations at sea meant observations at sea, those referring to capes or
> beaches or islands are usually accompanied by descriptions of local flora
> fauna, meaning that the ship made a stop on land. Cook is also very good
> being specific about the layout of the land itself: islands often have
> western and eastern extremities, as does beaches and even inland sea
> (e.g. entrance to Queen Charlotte's Sound). And of course, much of this
> coordinates were meant to be incorporated into new maps, and so maps made
> immediately after the expedition are good sources for location.
> Nonetheless, the question about precision still remains: exactly how
> precisely can we assign modern/accurate coordinates to Cook's coordinates,
> so that the error calculation actually mean something. Admittedly, this
> problem made me break out in cold sweat throughout the project--especially
> when dealing with measurements based on dastardly vague "cape-this" and
> "cape-that". Here I assume that "cape", "bay", "point" refer to shores
> where Cook's ships harbored and where observations were made. I threw out
> locations when such "cape" "bay" or "point" referred to a wide stretch of
> land. For the locations I worked with, "north" vs "south" of a "bay" or
> "beach" is significant only in seconds of longitude. However, because
> Cook's measures were almost always precise only to minutes of longitude, I
> decided to allow this imprecision in seconds of longitude. This means I
> to round all error calculations to minutes of longitude rather than
> (unfortunately, not sure if this is acceptable methodology).
> The problematic nature of historical data demands careful handling. My
> experience with Cook's journals is definitely a learning process, and
> frustratingly layered by multiple attempts to redo things. To be honest,
> the "final turned-in" product is still not good, and the data could
> from additional cleaning and scrutiny. But I do believe that there is
> enough resources and primary documents out there to render this sort of
> error analysis meaningful. It just requires a lot of research and care.
>> wrote:> View and reply to this message: http://fer3.com/arc/m2.aspx?i=121820
>> I seem to recall that Cook's survey of the coast of the Northern Island
>> New Zealand was amazingly accurate in latitude, but that was offset by
>> 25 miles (from memory) in longitude. I recall that he landed at least
>> to make astronomical observations. No doubt somebody will be better
>> informed than I on this subject..
>> At 15:24 07/01/2013, you wrote:
>> I have a more general question:
>>> What observations of Cook's expedition from known places on land
>>> are available?
>>> Except Point Venus, Thaiti, that I know.