NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Transit of venus 1769
From: J Cora
Date: 2006 May 24, 21:10 -0500
From: J Cora
Date: 2006 May 24, 21:10 -0500
I am starting to read "the SHIP retracing Captain Cook's Endeavour Voyage" which I found while browsing the stacks at our local library.
On page 27 to summarize: by observing from different parts of the globe and measuring the time the planet venus took to cross the sun, it would enable the measurement of the suns diameter and also the earth's distance from the sun, the Astronomical Unit.
The observations of the transit of venus in tahiti were not as precise as hoped since the timing of when venus first met the suns disc could not be determined with accuracy as a halo due venus atmosphere and an optical effect called blackspot.
via google:
In 1672 Cassini and Richer measured the parallax of mars from two locations on earth and came up with the estimate for AU of 140 million kilometers which underestimates today accepted value by 7 percent.
based on his analysis of the 1769 transit of Venus, Thomas Hornsby wrote in 1771 that "The parallax on the 3d of June being 8.65'', the mean parallax will be found to be = 8.78''; and if the semidiameter of the Earth be supposed = 3985 English miles, the mean distance of the Earth from the Sun will be 93,726,900 English miles."
Today the AU is approx 92750760 miles
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To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
On page 27 to summarize: by observing from different parts of the globe and measuring the time the planet venus took to cross the sun, it would enable the measurement of the suns diameter and also the earth's distance from the sun, the Astronomical Unit.
The observations of the transit of venus in tahiti were not as precise as hoped since the timing of when venus first met the suns disc could not be determined with accuracy as a halo due venus atmosphere and an optical effect called blackspot.
via google:
In 1672 Cassini and Richer measured the parallax of mars from two locations on earth and came up with the estimate for AU of 140 million kilometers which underestimates today accepted value by 7 percent.
based on his analysis of the 1769 transit of Venus, Thomas Hornsby wrote in 1771 that "The parallax on the 3d of June being 8.65'', the mean parallax will be found to be = 8.78''; and if the semidiameter of the Earth be supposed = 3985 English miles, the mean distance of the Earth from the Sun will be 93,726,900 English miles."
Today the AU is approx 92750760 miles
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---
