by neufer » Sat Sep 18, 2010 12:36 pm
Code: Select all
moon/ angular Magnitude
planet size
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Ganymede 1.9" 4.61 1610
Io 1.3" 5.02 1610
Europa 1.1" 5.29 1610
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Uranus 4.1" 5.32 1781
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Callisto 1.7" 5.65 1610
Titan 0.9" 8.20 1655
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Uranus is visible to the naked eye, has a fair amount of parallax (in just 4 days!) and sits right on the ecliptic where people have recorded the motions of Saturn & Jupiter for millennia. They even recorded the some of Saturn & Jupiter's moons since 1610/1655.
So why did it take until 1781 (171 years after Galileo) to discover Uranus
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- ___ King Lear > Act I, scene V
Fool: The reason why the seven stars
. are no more than seven is a pretty reason.
KING LEAR: Because they are not eight?
Fool: Yes, indeed: thou wouldst make a good fool.
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http://en.wikipedia.org/wiki/Uranus wrote:
<<Sir William Herschel observed the planet on 13 March 1781 while in the garden of his house at 19 New King Street in the town of Bath, Somerset (now the Herschel Museum of Astronomy), but initially reported it (on 26 April 1781) as a "comet". Herschel "engaged in a series of observations on the parallax of the fixed stars", using a telescope of his own design.
He recorded in his journal "In the quartile near ζ Tauri … either Nebulous star or perhaps a comet". On March 17, he noted, "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place". When he presented his discovery to the Royal Society, he continued to assert that he had found a comet while also implicitly comparing it to a planet:
“ The power I had on when I first saw the comet was 227. From experience I know that the diameters of the fixed stars are not proportionally magnified with higher powers, as planets are; therefore I now put the powers at 460 and 932, and found that the diameter of the comet increased in proportion to the power, as it ought to be, on the supposition of its not being a fixed star, while the diameters of the stars to which I compared it were not increased in the same ratio. Moreover, the comet being magnified much beyond what its light would admit of, appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain. The sequel has shown that my surmises were well-founded, this proving to be the Comet we have lately observed. ”
Herschel notified the Astronomer Royal, Nevil Maskelyne, of his discovery and received this flummoxed reply from him on April 23: "I don't know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it">>
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[code]moon/ angular Magnitude
planet size
-----------------------------------------
Ganymede 1.9" 4.61 1610
Io 1.3" 5.02 1610
Europa 1.1" 5.29 1610
.......................................
Uranus 4.1" 5.32 1781
.......................................
Callisto 1.7" 5.65 1610
Titan 0.9" 8.20 1655[/code]
---------------------------------------------------------------
Uranus is visible to the naked eye, has a fair amount of parallax (in just 4 days!) and sits right on the ecliptic where people have recorded the motions of Saturn & Jupiter for millennia. They even recorded the some of Saturn & Jupiter's moons since 1610/1655.
So why did it take until 1781 (171 years after Galileo) to discover Uranus :?:
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[list]___ King Lear > Act I, scene V
Fool: The reason why the seven stars
. are no more than seven is a pretty reason.
KING LEAR: Because they are not eight?
Fool: Yes, indeed: thou wouldst make a good fool.[/list]---------------------------------------------------------------
[quote=" http://en.wikipedia.org/wiki/Uranus"]
<<Sir William Herschel observed the planet on 13 March 1781 while in the garden of his house at 19 New King Street in the town of Bath, Somerset (now the Herschel Museum of Astronomy), but initially reported it (on 26 April 1781) as a "comet". Herschel "engaged in a series of observations on the parallax of the fixed stars", using a telescope of his own design.
He recorded in his journal "In the quartile near ζ Tauri … either Nebulous star or perhaps a comet". On March 17, he noted, "I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place". When he presented his discovery to the Royal Society, he continued to assert that he had found a comet while also implicitly comparing it to a planet:
“ The power I had on when I first saw the comet was 227. From experience I know that the diameters of the fixed stars are not proportionally magnified with higher powers, as planets are; therefore I now put the powers at 460 and 932, and found that the diameter of the comet increased in proportion to the power, as it ought to be, on the supposition of its not being a fixed star, while the diameters of the stars to which I compared it were not increased in the same ratio. Moreover, the comet being magnified much beyond what its light would admit of, appeared hazy and ill-defined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain. The sequel has shown that my surmises were well-founded, this proving to be the Comet we have lately observed. ”
Herschel notified the Astronomer Royal, Nevil Maskelyne, of his discovery and received this flummoxed reply from him on April 23: "I don't know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it">>[/quote]---------------------------------------------------------------