A historian friend is looking for a help in analysing Magellan’s Navigation - any suggestions?

The Vikings had a means of measuring the elevation of the sun, but it wasn't calibrated - you could use it to check if you were on the latitude of a place you'd previously visited, but not measure the latitude. It was basically a rectangle of wood on a string; you held the end of the string at your nose, and one edge of the wood was on the horizon and the other on the relevant celestial body. The length of the string fixed the angle. If used with Polaris, it would be reasonably reliable.
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Yes, but it required you to revisit your destination at or near enough the same time of year as you made your previous stop over. This was not considered too much of a problem as going "viking" was done in "season" and chances were that declination at noon would have been close-ish.
Without knowing your declination even sighting Polaris will not be much help.
 
Gary Fox said:
Do we know details of the instuments he had on board?
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A banjo and a Jew's Harp, according to legend. ;)

newtothis said:
And when leading historians say a book on their specialist subject written by a not very successful submariner who left school at 15 is rubbish, I tend to go with the historians.
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Speaking as someone who is not a very successful submariner* and who left school at 15, I resemble that remark! :D

(*or, indeed, any sort of submariner!)
 
Laminar Flow said:
The Vikings had a means of measuring the elevation of the sun, but it wasn't calibrated - you could use it to check if you were on the latitude of a place you'd previously visited, but not measure the latitude. It was basically a rectangle of wood on a string; you held the end of the string at your nose, and one edge of the wood was on the horizon and the other on the relevant celestial body. The length of the string fixed the angle. If used with Polaris, it would be reasonably reliable.
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Yes, but it required you to revisit your destination at or near enough the same time of year as you made your previous stop over. This was not considered too much of a problem as going "viking" was done in "season" and chances were that declination at noon would have been close-ish.
Without knowing your declination even sighting Polaris will not be much help.
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Best movie theme ever.

 
A quick dip into 'A History of the Practice of Navigation' by Hewson yielded this in the 'Log Line and Log Book' chapter.

'The first certain evidence of its (... the log ship's ..) employment is, according to Alexander Humbolt , to be found in Antonio Pigafetta's ship's journal of Magellan's voyage in an entry for the month of January , 1521. Neither Columbus nor Vasco da Gama , nor any other navigators prior to that date , mentioned its use.'

Moving right along - this chart Un Carta de Magallanes por la ruta de Tierra del Fuego which is dutch but dated not long after is interesting.
It shows longitude measured eastabout but gives Cabo de Virgines (sp) as about 303* 40' or 56*20'W.
Actual position is about 68* 20'W but back then they were measuring their longitude from their European departure point.

Accurate navigation in those days? If I find time I'll be back tomorrow with an interesting trip in 1683.
 
Frank Holden said:
A quick dip into 'A History of the Practice of Navigation' by Hewson yielded this in the 'Log Line and Log Book' chapter.

'The first certain evidence of its (... the log ship's ..) employment is, according to Alexander Humbolt , to be found in Antonio Pigafetta's ship's journal of Magellan's voyage in an entry for the month of January , 1521. Neither Columbus nor Vasco da Gama , nor any other navigators prior to that date , mentioned its use.'

Moving right along - this chart Un Carta de Magallanes por la ruta de Tierra del Fuego which is dutch but dated not long after is interesting.
It shows longitude measured eastabout but gives Cabo de Virgines (sp) as about 303* 40' or 56*20'W.
Actual position is about 68* 20'W but back then they were measuring their longitude from their European departure point.

Accurate navigation in those days? If I find time I'll be back tomorrow with an interesting trip in 1683.
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As you say, "accurate navigation" wasn't a thing until the 18th century, and most navigators would reckon longitude as so far east or west of their port of origin. Remember too that even land surveys were subject to substantial errors over the extent of a country; the first accurate map of France, for example, was Cassini's survey in 1745, and that was one of the first surveys that would be regarded as adequate by modern standards (there's a story that the King of France at the time complained that he'd lost more land to the surveyors than he's lost by war!). Unraveling the accounts of navigators before Cook is very much a guessing game. To this day, scholars are trying to determine (for example) Columbus' track - there is agreement on the fundamentals, but the detail is obscure in places. It's interesting to read Cook's accounts of trying to verify discoveries of land by previous explorers - their longitude was usually off by large amounts (ten or more degrees) in the cases where he found them. There are all sorts of "phantom" islands that were reported and then lost - mainly because they simply weren't anywhere near the longitude they were reported in. There are also issues to do with state security! In the 16th and 17th centuries, there is evidence that public accounts of voyages like Magellan's and Drake's were deliberately falsified to prevent others from following in their track! Routes and pilotage directions were valuable commercial secrets in those days. Even Cook's first voyage went out under false pretences; the ostensible aim was to observe the transit of Venus at Tahiti, but Cook's secret orders were to find and claim Terra Australis (which he showed didn't exist!)

Even to this day, I have investigated placenames in Antarctica, and many places named by early expeditions simply don't exist in the position they are reported at. Navigation in the 40s and 50s was still primarily dead reckoning (even in aircraft) and there were large errors such that it is impossible to align the features they named with modern mapping.
 
About the voyage I mentioned yesterday.
In 1680 a group of English pirates crossed Panama, pinched a spanish ship, and embarked on a bit of very successful pillaging and plundering along the west coast of south america.
Two years later - on the 5th November 1681 - they departed Isla Duque de York in what is now Chilean Patagonia and became the first englishmen to double Cape Horn eastwards. They rounded about 150 miles south of the Horn in 58* 20' S, further south than Drake had been and went on to make a safe landfall on Barbados in January 28th 1862 after almost 2 months out of sight of land.
Latitude sailing was employed at the end, having reached 13*10'N they turned left and sailed with the trades on their quarter for the last 10 days.
The ship was 'Trinity' , Captain Sharp. Read all about it in 'A Buccaneer's Atlas, Basil Ringrose's South Sea Waggoner'.
 
Frank Holden said:
About the voyage I mentioned yesterday.
In 1680 a group of English pirates crossed Panama, pinched a spanish ship, and embarked on a bit of very successful pillaging and plundering along the west coast of south america.
Two years later - on the 5th November 1681 - they departed Isla Duque de York in what is now Chilean Patagonia and became the first englishmen to double Cape Horn eastwards. They rounded about 150 miles south of the Horn in 58* 20' S, further south than Drake had been and went on to make a safe landfall on Barbados in January 28th 1862 after almost 2 months out of sight of land.
Latitude sailing was employed at the end, having reached 13*10'N they turned left and sailed with the trades on their quarter for the last 10 days.
The ship was 'Trinity' , Captain Sharp. Read all about it in 'A Buccaneer's Atlas, Basil Ringrose's South Sea Waggoner'.
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A bit of a different situation to Magellan's time. By 1680 navigational instruments had evolved significantly, as had the use of tables of declination to establish noon latitude. Additionally, reaching the trades and then turning left towards a well-known destination in what was by then a commonly understood Atlantic weather pattern would have helped as well. And, finally, the islands can be spotted some 50 miles out by identifying the cloud formations over them.

Old Magellan had none of these aids when he set out across the (to Europeans) unknown Pacific.
 
Roberto said:
Original document (in Spanish):
http://sevilla.2019-2022.org/wp-con...villa2019_Derrotero-de-Francisco-Albo-f15.pdf
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I see in that document that the longitude of Cabo de Virgines is given as 52* 1/2 which suggests they had taken their 'departure' from Teneriffe ie about 16*40' W which - when combined - gives us 69* 10'W which is pretty close to today's longitude of about 68* 1/2 W.

That seems reasonably accurate to me.... did they confirm their longitude while at Rio de Janeiro?
 
Frank Holden said:
I see in that document that the longitude of Cabo de Virgines is given as 52* 1/2 which suggests they had taken their 'departure' from Teneriffe ie about 16*40' W which - when combined - gives us 69* 10'W which is pretty close to today's longitude of about 68* 1/2 W.

That seems reasonably accurate to me.... did they confirm their longitude while at Rio de Janeiro?
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By the time Magellan left, the Portuguese had already explored and mapped out much of the Atlantic and Eastern South America. The only question in this context is, how much of this was known to Magellan, sailing under Spanish flag.
 
Laminar Flow said:
By the time Magellan left, the Portuguese had already explored and mapped out much of the Atlantic and Eastern South America. The only question in this context is, how much of this was known to Magellan, sailing under Spanish flag.
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It is said that Columbus was fed mis-information by the Portuguese who had already been to the West Indies and India.
 
25931 said:
It is said that Columbus was fed mis-information by the Portuguese who had already been to the West Indies and India.
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I do not know that, or rather, I have not seen any evidence to support this. Vasco da Gama reached India in 1496 to cut out the middlemen on the overland trade routes. While both Columbus, 1492 and Magellan, 1521 sought to circumvent Portuguese dominance of the route around Africa by heading west.
 
Laminar Flow said:
Before my first ocean crossing I was quite anxious about my navigation. I asked another sailor, while we were in the Canaries, how he managed: "Oh," said he, "every few days I take a noon sight, that's good enough. Besides, when you cross an ocean, you are bound to hit land somewhere on the other side." He went on to tell me he had lost 5 boats in his sailing career which gives me little confidence in this methodology.
Even with the most careful practice, navigation by deadreckoning is uncomfortably inaccurate. Sure, you will eventually hit land, the question is when and where.
The entrance to the Straight of Juan de Fuca in the Pacific North West is a prime example: The target is a mere 30 miles wide and there are, quite literally, hundreds of wrecks either side, of ships approaching from the open Pacific and that were unable to fix their position, possibly for days or weeks, due to the frequently overcast skies.
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Any damn fool(and anyone looking to do anything other is a damn fool) attempting such a land fall without planning on 'hitting' the land to one side or the other of the desired 'hole' is definitely a damn fool. Always plan on the basis of the worst possible expected accuracy, not the best; wise human beings know they're going to be inaccurate so embrace your fallibility.
 
penfold said:
Any damn fool(and anyone looking to do anything other is a damn fool) attempting such a land fall without planning on 'hitting' the land to one side or the other of the desired 'hole' is definitely a damn fool. Always plan on the basis of the worst possible expected accuracy, not the best; wise human beings know they're going to be inaccurate so embrace your fallibility.
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Safely ensconced in a world ruled by GPS and declaring hindsight is cheap business.
Indeed, anyone heading across the North Sea or even the Atlantic with just a free road map issued by the local automobile club, is a lot better equipped and better informed than any of the early navigators.
Additionally, you do not appear to have much a concept of astronomical navigation or it's inherent limitations. Until fairly recently, being within 50 miles of where you thought or hoped you were, was pretty good going. Missing a thirty mile wide target on a dangerous coast, beset with fog, impenetrable rain, frequent storms, possibly at night, is easily achieved, even with the best of navigational skills and the greatest precautions. Many old charts showed at silhouette of the land as would have been seen upon approach; just too damn bad in poor visibility and if you had not been able to take a sight for some days. Shame they didn't have you on board; the amount of heart break that could have been avoided.
 
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