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Old 30-07-2020, 21:56   #16
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Re: wood ships , iron men

Nevil Maskelyne has gotten an undeserved bad rap - and Sobel's book isn't helping matters. Remember that Maskelyne (as a member of the board of longitude) was not eligible for the prize. And he had already developed his lunar method and proved that it worked. In the brief interim between the advent of lunars and the widespread availability of chronometers, Maskelyne's method was in regular use. And as "Astronomer Royal", he had already established himself and had many other projects on his plate. So what reason would he have for trying to suppress Harrison's invention? None, really.



In fact, Maskelyne himself wrote in 1800 that he "... always allowed Mr. Harrison's great merit, as a genius of the first rate, who had discovered, of himself, the causes of the irregularities of watches, and pointed out the means of correcting these errors in a great degree, in the execution of a portable time-keeper, of a moderate size, to be put on board of ship, not liable to disturbance from the motions of the ship, and exact enough to keep time within two minutes in six weeks."


Nevil Maskelyne was not an evil villain. And John Harrison was not a persecuted saint. They were both complex yet ordinary people. And they both contributed greatly to the advancement of ocean navigation. Some historians and authors are beginning to realize this and are finally working to try and repair Maskelyne's reputation. You can find some of their work online in the usual way.
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Old 30-07-2020, 22:23   #17
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Re: wood ships , iron men

https://maas.museum/observations/200...his-longitude/
James Cook had no chronometer on his 1st voyage but did on later voyages. Polynesians surprised them by doing triangulation off the top of their head.

"These Polynesians.. .knowledge was .. extremely detailed, very accurate and in many respects superior to the instruments of the western navigators, such as Magellan and Cook, for whom the Pacific was a sea of constant surprises... western European sailors did not venture deep into their neighbourhood until the end of the Middle Ages. .they learned the art of dead reckoning, judging distance as they sailed to gain some sense of longitude: they appear to have found this easier to do than European sailors, who had to await the invention of the chronometer.. Tupaia , a Polynesian navigator who accompanied Captain Cook, astonished Cook's companions by his almost instinctive awareness of where the ship stood, without instruments or written records...just the super computer of the human brain. One of the most extraordinary methods of navigation was .a system known in the Carolina Islands as etak...a relationship ..between the destination and another island in its vicinity; the method depended on placing this third point accurately in relation to the stars... powerful mental geometry , not to mention an astonishingly detailed, carefully memorised, mobile map of the heavens. _ D Abulafia 2019. "The Boundless Sea". Allen Lane. pp 5, 16-19. (Mediterranean History , Cambridge University).
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Old 31-07-2020, 00:40   #18
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Re: wood ships , iron men

Harrisons Chronometers no. 1,2,3, and 4 can still be seen at the Observatory in Greenwich. I was there in 1978. Very impressive.
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Old 31-07-2020, 00:54   #19
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Re: wood ships , iron men

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Harrisons Chronometers no. 1,2,3, and 4 can still be seen at the Observatory in Greenwich. I was there in 1978. Very impressive.
I used to walk past it twice a day when I lived on one side of the world and worked on the other.

Funniest moment I remember was seeing a foreign tourist in front of the clock, checking his watch, say “hmmm, it’s wrong”. Errr, I don’t think it’s possible to say that when looking at the Greenwich Observatory clock... that’s what time is.
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Old 31-07-2020, 11:08   #20
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Re: wood ships , iron men

In 1304 , Dante wrote in "Divine Comedy" that the Southern ocean was empty of people and there was a polar mountain . That's opposite to the geography of the north pole region and unlikely to be just a guess. Arabs traded with 'Indonesia' and with Venice where Dante was an ambassador.

In 1810 the first known ship at Macquarie island S of New Zealand, reported a "ship of ancient design" , 20 years after British settlement in Australia.

It could be that the southern seas were well-travelled and Cook came centuries after the other explorers to the Antarctic.
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Old 31-07-2020, 19:19   #21
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Re: wood ships , iron men

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Originally Posted by fouled View Post
https://maas.museum/observations/200...his-longitude/
James Cook had no chronometer on his 1st voyage but did on later voyages. Polynesians surprised them by doing triangulation off the top of their head.

"These Polynesians.. .knowledge was .. extremely detailed, very accurate and in many respects superior to the instruments of the western navigators, such as Magellan and Cook, for whom the Pacific was a sea of constant surprises... western European sailors did not venture deep into their neighbourhood until the end of the Middle Ages. .they learned the art of dead reckoning, judging distance as they sailed to gain some sense of longitude: they appear to have found this easier to do than European sailors, who had to await the invention of the chronometer.. Tupaia , a Polynesian navigator who accompanied Captain Cook, astonished Cook's companions by his almost instinctive awareness of where the ship stood, without instruments or written records...just the super computer of the human brain. One of the most extraordinary methods of navigation was .a system known in the Carolina Islands as etak...a relationship ..between the destination and another island in its vicinity; the method depended on placing this third point accurately in relation to the stars... powerful mental geometry , not to mention an astonishingly detailed, carefully memorised, mobile map of the heavens. _ D Abulafia 2019. "The Boundless Sea". Allen Lane. pp 5, 16-19. (Mediterranean History , Cambridge University).
They were great navigators, unfortunately it required a mass of local knowledge as well as half a lifetime of experience acquired judgement. The European technique using chronometer and sextant and and celestial observations allowed thousands of relatively inexperienced youthful seamen to be fairly quickly taught to locate a position anywhere on the planet. Coupled with reasonably accurate charts any ships captain could navigate to ports in places never before visited.

Polynesian navigators discovered the Pacific, western navigators the seas and oceans of world - both were magnificent achievements.
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Old 31-07-2020, 20:05   #22
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Re: wood ships , iron men

Clocks are cool and all that but are basically useless with out the work of Johannes Müller von Königsberg AKA Regiomontanus. His development of the first useful ephemeris was the key to navigation in the age of discovery. Arne Molander details in his book how Columbus used Muller's ephemeris to stay on the same longitude in his first voyage to the Americas (really the Bahamas). There was a star that stayed five degrees above the horizon the entire trip and Columbus used what was basically a protractor to keep the star close to five degrees once he got on the right longitude.

No question the development of protractors into sextants and good clocks helped; but again both would be useless without the continued improvements in Muller's ephemeris.
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Old 31-07-2020, 22:17   #23
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Re: wood ships , iron men

Here is a timeline I made of some notable events concerning time and longitude. (Warning: the full size image is very large.)






I was trying to get a general idea of how things progressed, but this diagram is certainly not exhaustive. In retrospect, I should have included the actual year in each event's description. But you get the idea.
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Old 31-07-2020, 23:58   #24
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Re: wood ships , iron men

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Originally Posted by tomfl View Post
Clocks are cool and all that but are basically useless with out the work of Johannes Müller von Königsberg AKA Regiomontanus. His development of the first useful ephemeris was the key to navigation in the age of discovery. Arne Molander details in his book how Columbus used Muller's ephemeris to stay on the same longitude in his first voyage to the Americas (really the Bahamas). There was a star that stayed five degrees above the horizon the entire trip and Columbus used what was basically a protractor to keep the star close to five degrees once he got on the right longitude.
1. You are confusing longitude with latitude.

2. A star can't stay "5 degrees above the horizon". It can however reach a maximum of five degrees above the horizon once each night but it would be below the horizon much of the time.


3. Astrolabes were in use many hundred of years before Coolumbus.
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Old 01-08-2020, 01:23   #25
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Re: wood ships , iron men

Well, Polaris would stay [roughly] 5° above the horizon at 5° north latitude.
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Old 01-08-2020, 08:54   #26
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Re: wood ships , iron men

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Well, Polaris would stay [roughly] 5° above the horizon at 5° north latitude.

Doh! That's what you get when thinking from a southern hemisphere perspective. I didn't think of the special case of Polaris.



(But that would have had him making landfall in what is now French Guiana )
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Old 01-08-2020, 09:51   #27
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Re: wood ships , iron men

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1. You are confusing longitude with latitude.

2. A star can't stay "5 degrees above the horizon". It can however reach a maximum of five degrees above the horizon once each night but it would be below the horizon much of the time.


3. Astrolabes were in use many hundred of years before Coolumbus.
Picky, picky, picky. My bad and what you posted is true; but completely missed the point of my post.

With out an ephemeris nothing else matters.
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Old 01-08-2020, 15:15   #28
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Re: wood ships , iron men

In 1300 Polaris was about 4 degrees off N and in 1304 Dante wrote of sailing in the south ocean where Polaris never rose. That's south from Kenya/ Tanzania . Arabs used a kamal piece of wood on a string held in the mouth to sight the north for latitude and had maps of southern Africa which Vasco da Gama borrowed.

https://archive.aramcoworld.com/issu....ibn.majid.htm

They probably worked with rhumb bearing lines instead of plotting lat. long. Using the Southern Cross would be not so easy.
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Old 01-08-2020, 16:44   #29
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Re: wood ships , iron men

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Also, with an estimate of longitude, the brits could start to plot out the major ocean currents far more accurately.
It is my understanding that the pioneer in establishing ocean currents was Matthew Fontaine Maury of the US Navy. He analyzed the logbooks from thousands of voyages that were sent to the US government but before Maury basically ignored.
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Old 01-08-2020, 17:34   #30
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Re: wood ships , iron men

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It is my understanding that the pioneer in establishing ocean currents was Matthew Fontaine Maury of the US Navy.

Speaking of Maury, the lake named in his honor - which is near America's national maritime museum, The Mariners Museum - has been renamed. Apparently his views on slavery completely nullify all of his accomplishments.
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