Thursday, May 30, 2019

Epic view of Moon transiting the Earth

This shot is beautiful and should be taught in any film studies class.
This animation features actual satellite images of the far side of the moon, illuminated by the sun, as it crosses between the DSCOVR spacecraft's Earth Polychromatic Imaging Camera (EPIC) and telescope, and the Earth - one million miles away.
NASA
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Wednesday, May 29, 2019

'Legendary' map of Pacific by James Cook's Tahitian navigator Tupaia finally unlocked

Tupaia's first draft map of the Pacific.
Copy of a Chart made by … Tupaïa’ by Georg Forster, 1776, Stadtarchiv Braunschweig 
Tupaia used the centre of his map as north, or noon, and the readings from north changed depending on which island you were on.

From Stuff by Anana- Zaki

The secret of a "legendary" map has finally been unlocked.

After six years of research, two German professors believe Tahitian navigator Tupaia's map of the Pacific, once thought to be "unreadable," was "fully understandable".
And in another "breakthrough", the Potsdam University researchers, Lars Eckstein​ and Anja Schwarz,​ believe the map, co-produced by Captain James Cook, was completed when Cook's ship the Endeavour was anchored at Queen Charlotte Sound.
Schwarz said she "firmly believed" their views about the 248-year-old map, and they had evidence to back up their theories.

Cook joined the British merchant navy as a teenager and joined the Royal Navy in 1755.
He saw action.

Tupaia took part in Cook's first voyage as a navigator and translator, and was "highly regarded" by the Endeavour captain, and drew the map between 1769 and 1770, she said.
"This map was co-produced by many people including Cook, and although not very well known, has been written about in the past. It's usually been written about in two primary ways.
"One way was, Tupaia showing his knowledge of the Pacific. Another way it has been read is, Tupaia knew of these places but he didn't know where they were, and half of the places didn't exist and the names were all wrong," Schwarz said.
But for Schwarz and Eckstein, the map made "a lot of sense".

 Tupaia’s Map, 1770, British Library, London


A reworked version of Tupaia's map, which numbers the islands in the order Cook and his crew visited them on their first voyage.

"It was meant to be read and we just had to figure out how to do it," Schwarz said.
To begin understanding the map, the researchers had to put their minds in the "Polynesian way of navigating".
According to Eckstein, when compared to Europeans, the Polynesians took a very different approach to travelling and mapping where they were in the world.

A replica of the Endeavour in Poverty Bay on the east coast of the North Island.

"Europeans abstract space, they objectivise it, externalise it and fix it. They then measure it with the invisible lines of latitude and longitude, measure where you are and then travel," he said.
Polynesians imagined a world where "people didn't move", but the "world moved around them", Eckstein said.
"If you know your bearings, the sea will throw out the island from the horizon and bring it to you. You see how completely opposite those kinds of world views are?

This is Tahitian high priest and navigator Tupaia’s only known drawing of New Zealand. A remastered drawing by Tupaia depicting an unknown Māori and naturalist Joseph Banks exchanging a crayfish and what is believed to be a tapa (bark) cloth. 

"The idea with Polynesian navigators is that the world is not fixed, the world constantly moves," he said.

The beginning of Tupaia's map being drawn up was when the Endeavour left the Pacific Islands in search of Australia in 1769, after extensively touring the region with the help of the Tahitian.
"So they left that world, and that was the moment Cook said to Tupaia, 'you've told us about all those islands, why don't you draw a chart for us?'.
"This is how the story unfolds," Eckstein said.

An "important find" in the research was German explorer Georg Forster's copy of Tupaia's first draft map of the Pacific.
Forster took part in Cook's second voyage to the Pacific.

A list of Pacific Islands supplied by Tupaia in the order they were sighted by the Endeavour.
Robert Molyneux’s Master’s Log, National Archives Kew, London 

He said Forster's copy "helped understand" how Tupaia's map began.
"What would have happened is, sitting around the drawing table in Cook's cabin aboard the Endeavour, the Europeans take out an empty sheet of paper, they drew the cardinal points and they would have indicated north, east, south, west.
"They begun by drawing all the islands that they had themselves seen on the first voyage in 1769," Eckstein said.

After the Endeavour officers added their own islands onto the map, they handed it over to Tupaia to complete, due to the Tahitian's extensive knowledge of the Pacific, he said.

 Voyaging paths on Tupaia’s Map; visualized on the British Library copy

 Voyaging paths on Tupaia’s Map, as shown on a Mercator Map of Oceania.

Mercator Map of Oceania with the GeoGarage platform (UKHO map)
Extract from David Rumsey maps collection
overlaid on Google Maps with the GeoGarage platform

But instead of following the European approach to navigation, Tupaia used the Polynesian method, Eckstein said.

The researchers first used a list of islands written down by Tupaia, which he listed in the order the Endeavour sighted them.
They then numbered the islands in that order, and translated the numbers onto Tupaia's map, and that was the "magic moment", Eckstein said.
"What seems to be chaotic, suddenly resolves into some form of order.
"So you can see the six, seven, eight, nine, something [is] happening there. There are sequences all over the map."

Why were the researchers so sure of this?
It was due to another "major discovery".

 Rima-roa, five captions and three ships

 Avatea

The discovery was around the word Avatea​, which appeared on the centre of the map.
"Avatea in Tahitian, according to the European vocabulary lists, means noon. Noon is marked by the pinnacle position of the sun in the daily course of the sun's movements.
"For some reason, Tupaia chose to place that word at the very centre of the map," Eckstein said.

The researchers believed that reason was due to a daily "ritual" on board the Endeavour, which happened at noon.
"Everyday at noon, all the officers had to report on deck, all the precious instruments like sextants would be brought on deck and checked.
"So Tupaia would have seen this everyday on board," Eckstein said.
That was how Avatea came about, he said.


Come with us on Cook's world-changing expeditions.
Trace their routes and find out the ambitious aims behind them.
Continue your journey into their impact and legacy on the British Library website.

Using the Polynesian approach to navigation, the researchers came up with the theory that every island on the map was in fact the centre, in Tupaia's view.
"From the centre, you can get your bearings by looking at noon.
"The European north was the noon [Avatea] on the map, and you could calculate the bearings by using the island and pointing to the map's centre," Eckstein said.
By using this technique, the map's bearings could be figured out, he said.
"If you want to go from Rarotonga and want to go to Tonga, you go west," Eckstein said.

But "unfortunately" for New Zealand, it was not included in the map.
However, the researchers believed the map was finished in the country, when Cook anchored at Ship Cove.
"We firmly believe this map was finished here in New Zealand and there are several indicators of that," Schwarz said.

Created by Dutch explorers, this incredible map shows European knowledge of the Pacific
prior to Cook’s voyages in the 18th century.

In one of the copies of Cook's manuscripts, the admiralty copy, he listed islands sighted by Tupaia and the Endeavour, and he included a version of the map, which included New Zealand, Schwarz said.

1784 map of the Pacific Ocean showing the routes of explorers

on 8th Oct. 1769 Captain James Cook landed in New Zealand
National Archive 

Chart of New Zealnd, explored in 1769 and 1770 by Lieutenant J. Cook, engraved by I. Bayly

The researchers believed the manuscript with the map that included New Zealand was finished while the Endeavour was anchored in the Queen Charlotte Sound, because that was the only way Cook "would have had the time" to do so, Schwarz said.

But Eckstein and Schwarz said they were still researching the theory surrounding the last known location of where the map was finished, but they were "confident" in their theory.
The researchers toured New Zealand in February this year to present their findings and theories.

Who is Tupia ?
  • He was a Tahitian navigator who sailed aboard the Endeavour in Captain Cook's first voyage.
  • He also acted as a translator in Cook's encounters with Māori.
  • It was thought he was born around 1724-25 and died in 1770 from an illness, he was buried in an unknown grave on the island of Damar-Besar, Indonesia.
  • There are no known drawings or paintings of him.
  • He was not only known for his navigation skills, but was known for his knowledge on genealogy and spirituality.
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Tuesday, May 28, 2019

L'Hermione ship leaving Nantes

localization of L'Hermione with the Weather4D R&N iOS mobile app,
through a AIS data flow provided by the GeoGarage AIS antenna
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SpaceX's bright Starlink satellites won't ruin the night sky


SpaceX’s goal is to launch a total of 720 satellites by the end of the 2020,
and eventually increase the number to more than 4,000.

From Space by
 
Musk says Starlink won't mess up astronomy.

The brilliant "train" in the night sky that is SpaceX's first 60 Starlink satellites has wowed some skywatchers, but it also sparked concern among some astronomers wondering what so many visible satellites could mean for scientific observing.


A swarm of Starlink satellites in the sky over Russia.

SpaceX CEO Elon Musk, it seems, is listening.


Musk wrote on Twitter today (May 27) that he's already instructed teams to look into making future Starlink internet communications satellites less shiny to lower their "albedo," or reflectivity. He pointed that out in response to a direct call from a com menter on Twitter.

"Agreed, sent a note to Starlink team last week specifically regarding albedo reduction," Musk wrote. "We'll get a better sense of value of this when satellites have raised orbits & arrays are tracking to sun."

(Image: © SpaceX)
A view of SpaceX's first 60 Starlink satellites in orbit, still in stacked configuration,
with the Earth as a brilliant blue backdrop on May 23, 2019.
SpaceX launched the Starlink satellites Thursday (May 23) into an initial orbit 273 miles (440 kilometers) above Earth. Each satellite is equipped with Krypton ion thrusters to raise its orbit to a final 342 miles (550 km).

"I know people are excited about those images of the train of SpaceX Starlink satellites, but it gives me pause," planetary astronomer Alex Parker wrote on Twitter Saturday (May 25) as the first videos of the Starlink "train" were popping up.
"They're bright, and there are going to be a lot of them."
The Starlink satellites are the vanguard of a planned 12,000-satellite megaconstellation designed to offer affordable internet service to people around the world who otherwise would not have such access.

 Space debris
(image : Southampton University)

Parker added that 12,000 bright satellites could potentially outnumber the stars visible to the unaided eye in the night sky.
But he was holding off on any final judgement until the Starlink satellites reached their final orbit, as they may be less visible at that time.

In a series of Twitter posts today, Musk assured astronomers and the public that the Starlink constellation shouldn't pose an issue for astronomy.

"Exactly, potentially helping billions of economically disadvantaged people is the greater good," Musk wrote in response to a comment on the service Starlink's constellation would provide. "That said, we'll make sure Starlink has no material effect on discoveries in astronomy. We care a great deal about science."

SpaceX’s Starlink is a next-generation satellite network capable of connecting the globe, especially reaching those who are not yet connected, with reliable and affordable broadband internet services.

And the satellites can be moved to reduce reflectivity, he added.
"If we need to tweak sat orientation to minimize solar reflection during critical astronomical experiments, that's easily done," Musk wrote.

Starlink shouldn't affect radio astronomy research either, Musk added.
"We avoid use of certain lower Ku frequencies specifically for radio astronomy," he wrote.
And then there's all those other satellites up in space, he added.
"There are already 4,900 satellites in orbit, which people notice ~0% of the time,"Musk wrote. "Starlink won't be seen by anyone unless looking very carefully & will have ~0% impact on advancements in astronomy."

Fraser Crain of Universe Today suggested to Musk that SpaceX consider using the Starlink satellite chassis for small space telescopes as an olive branch to the astronomy community.
"Would love to do exactly that," Musk replied.

Live view of 800 satellites in activity
(source satmap.space)

SpaceX is not the only company developing megaconstellations of internet satellites.
OneWeb launched the first six satellites of a planned 648-satellite constellation earlier this year. Telesat is aiming to build a 292-satellite network, while Amazon has unveiled plans for its own 3,236-satellite constellation.

Meanwhile, Starlink's first 60 satellites should remain visible over the next few days as they raise their orbits. Here's a guide on how to see Starlink in the night sky from our columnist Joe Rao.

"The Starlink satellites just passed directly overhead. They were glinting, some as bright as Polaris," Parker wrote Sunday night.
"Quite an eerie looking thing. And yes, the stars are out."

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Monday, May 27, 2019

British Isles & misc. (UKHO) update in the GeoGarage platform

34 nautical charts updated
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