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Equation of Time



 
 
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  #1  
Old April 25th 08, 12:47 PM posted to uk.sci.astronomy
Les Desser
external usenet poster
 
Posts: 15
Default Equation of Time

I am preparing a presentation on the Equation of Time and have been
trying to find a clear description, preferable with diagrams, of the
adjustment due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I
still find it inadequate.

The example of the bus going down the incline is good to show the
slowdown but I cannot find anything appropriate to explain the speeding
up.

Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)
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  #2  
Old April 25th 08, 04:12 PM posted to uk.sci.astronomy
oriel36[_2_]
external usenet poster
 
Posts: 8,478
Default Equation of Time

On Apr 25, 12:47*pm, Les Desser wrote:
I am preparing a presentation on the Equation of Time and have been
trying to find a clear description, preferable with diagrams, of the
adjustment due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I
still find it inadequate.

The example of the bus going down the incline is good to show the
slowdown but I cannot find anything appropriate to explain the speeding
up.

Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)


There is only one accurate explanation of the Equation of Time in
existence and even that is incomplete -

http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html


The Equation of Time creates the 24 hour day out of the natural noon
cycle -

"the Earth...makes an entire revolution in the Ecliptick in 365 days,
5 hours 49 min. or there about, and that those days, reckon'd from
noon to noon, are of different lenghts; as is known to all that are
vers'd in Astronomy. Now between the longest and the shortest of those
days, a day may be taken of such a length, as 365 such days, 5. hours
&c. (the same numbers as before) make up, or are equall to that
revolution: And this is call'd the Equal or Mean day, according to
which the Watches are to be set; and therefore the Hour or Minute
shew'd by the Watches, though they be perfectly Iust and equal, must
needs differ almost continually from those that are shew'd by the
Sun,..But this Difference is regular, and is otherwise call'd the
Aequation," Huygens

The Equation of Time also keeps one of these 24 hour days elapsing
into the next 24 hour day,Monday into Tuesday ect.

When Copernicus discovered that the orbital motion of the Earth around
the central Sun accounted for the observed behavior of the other
planets,it left axial rotation to explain the daily cycle.When axial
rotation was discovered,the timekeeping astronomers applied the
Equation of Time (EOT) principles to terrestrial geometry and
geography,they did not have to assume axial rotation to be constant
but as the EOT facility which keeps the 24 hour day to natural
noon,they exploited this principle which allows axial rotation to be
considered constant as a convenience and not as an observation.It is
tricky the way it all works but the actual astronomical means is
nothing like the fiction of the NMM treatment.

It is absolutely crucial to understand what the Equation of Time
actually represents in terms of axial and orbital
motions,provisionally,it represents a rate of change using natural
noon as a benchmark without going into further details.

Of course most here do not recognise variations in the difference
between natural noon and 24 hour clock noon as the irreducable
complexity of the solar/sidereal fiction requires noon cycles to be
equal,the distance the Earth travels in its orbit must correspond
to .986 degrees/3 min 56 sec in order to conclude that the Earth
rotates through 360 degrees in 23 hours 56 minutes 04 seconds -

http://en.wikipedia.org/wiki/Image:T...3%A9reo.en.png

If you can explain the Equation of Time with the graphic above then
good for you,the fact that it is pure fiction hardly matters to those
who will comfortably give you advice in regards to the Equation of
Time yet still believe the Earth rotates through 360 degrees in 23
hours 56 minutes 04 seconds.Think of it as Piltdown man to the power
of 100 when you get your replies.



  #3  
Old April 25th 08, 08:15 PM posted to uk.sci.astronomy
OG
external usenet poster
 
Posts: 780
Default Equation of Time


"Les Desser" wrote in message
...
I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.

The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.

Has anyone seen and better presented explanations?


Does this have what you're looking for
http://www.analemma.com/
?


  #4  
Old April 26th 08, 09:25 AM posted to uk.sci.astronomy
Pd
external usenet poster
 
Posts: 17
Default Equation of Time

OG wrote:

Does this have what you're looking for
http://www.analemma.com/


Great explanation there, with lots of diagrams and animations. Nice
work.

--
Pd
  #5  
Old April 26th 08, 10:51 AM posted to uk.sci.astronomy
oriel36[_2_]
external usenet poster
 
Posts: 8,478
Default Equation of Time

On Apr 25, 8:15*pm, "OG" wrote:
"Les Desser" wrote in message

...





I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.


The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer


The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.


The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.


Has anyone seen and better presented explanations?


Does this have what you're looking forhttp://www.analemma.com/
?- Hide quoted text -

- Show quoted text -


Are you quite finished with this late 17th century nonsense ?.

If genuine and serious investigators could spot how Piltdown man was
a hoax then the astronomical equivalent is probably the sidereal/solar
fiction first and then this hoax known as the analemma.People who
promote variations in axial inclination to the Sun just do not know
any better and shouldfd be left to their own devices,you included.

The variations in natural noon cycle arise directly from the orbital
motion of the Earth,specifically the difference between constant axial
rotation and changing orbital oreintation as a component of orbital
motion,nothing more and nothing less.The Earth is not a machine where
its components act like cogs in a machine insofar as it is fine to
inspect the individual axial and orbital motions and orientations
and determine what effects they account for but the trouble is that
the reasoning which generates the 'analemma' hoax is based on combined
axial and orbital motions as a single compound motion.I do not know
how you manage to keep the Earth tilting back and forth to the Sun
while keeping its rotational orientation fixed to Polaris,but then
again,you reason off a constant 24 hour noon cycle,determine no
variations in orbital distance ect ,ect.The Equation of Time creates
the 24 hour day out of the determination of natural noon but somehow
you turn this around to use the 24 hour day to determine the location
of the Sun in the sky or the notorious figure - 8,for an astronomer
looking on ,at least one familiar with what the Equation of Time
does,this is bewildering.

In a few sentences ,the treatise of Huygens and his exposition of the
correct method jettisons this silly analemma attached to the Equation
of Time -

"Draw a Meridian line upon a floor (the manner of doing which is
sufficiently known; and note, that the utmost exactness herein is not
necessary and then hang two plummets, each by a small thred or wire,
directly over the said Meridian, at the distance of some 2. feet or
more one from the other, as the smalness of the thred will admit. When
the middle of the Sun (the Eye being placed so, as to bring both the
threds into one line) appears to be in the same line exactly you are
then immediately to set the Watch, not precisely to the hour of 12.
but by so much less, as is the Aequation of the day by the Table."
Huygens

http://www.xs4all.nl/~adcs/Huygens/06/kort-E.html

The length of time between the natural noon cycles change,the Equation
of Time equalises to variations to 24 hours and that is it.To turn
around and then say a 24 hour clock determines natural noon or some
irrelevent variation in inclination to the Sun is a product of a silly
imagination,again,Piltdown man comes to mind.


Anyone who finds substance in these analemmas things is not an
astronomer and I do not care how established they have become as a
'fact',even a brief reading of how to determine natural noon and then
apply the Equation of Time shopuld be definitive enough.







  #6  
Old April 26th 08, 12:04 PM posted to uk.sci.astronomy
Mike Dworetsky
external usenet poster
 
Posts: 715
Default Equation of Time

"Les Desser" wrote in message
...
I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.

The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.

Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)


I recommend the following web site:

http://www.analemma.com/

There is a diagram, possibly what you are looking for, that separates the
obliquity and eccentricity effects, at the Royal Observatory web site:

http://www.nmm.ac.uk/server/show/conWebDoc.351

Try also wikipedia on both topics.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #7  
Old April 26th 08, 12:09 PM posted to uk.sci.astronomy
Mike Dworetsky
external usenet poster
 
Posts: 715
Default Equation of Time

"Les Desser" wrote in message
...
I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.

The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer

The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.

The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.

Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)


Sorry, I realised that I sent in a page you already knew about!

Try the diagram on this one.

http://www.astronomynotes.com/nakedeye/s9.htm

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)

  #8  
Old April 26th 08, 12:55 PM posted to uk.sci.astronomy
oriel36[_2_]
external usenet poster
 
Posts: 8,478
Default Equation of Time

On Apr 26, 12:04*pm, "Mike Dworetsky"
wrote:
"Les Desser" wrote in message

...





I am preparing a presentation on the Equation of Time and have been trying
to find a clear description, preferable with diagrams, of the adjustment
due to obliquity.


The explanation at the National Maritime Museum
http://www.nmm.ac.uk/server/show/conWebDoc.351 only makes sense if you
already know the answer


The best I could find was the page at
http://www.wallingfordclock.talktalk.net/Sidereal%20Time.htm but I still
find it inadequate.


The example of the bus going down the incline is good to show the slowdown
but I cannot find anything appropriate to explain the speeding up.


Has anyone seen and better presented explanations?
--
Les Desser
(The Reply-to address IS valid)


I recommend the following web site:

http://www.analemma.com/

There is a diagram, possibly what you are looking for, that separates the
obliquity and eccentricity effects, at the Royal Observatory web site:

http://www.nmm.ac.uk/server/show/conWebDoc.351

Try also wikipedia on both topics.

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)- Hide quoted text -

- Show quoted text -


By all means keep the NMM explanation and especially this gem-

'The equation of time due to obliquity (the Earth's tilt) '

"The angle between the planes of the equator and the Earth's orbit
around the Sun is called the angle of obliquity.
If the Earth's rotation axis was not tilted with respect to its orbit,
the apparent motion of the Sun along the the Ecliptic would fall
exactly on the equator, covering equal angles along the equator in
equal time. "

http://www.nmm.ac.uk/server/show/conWebDoc.351

It would be really nicve to have adults who can openly discuss how
variations in daylight darkness North and South of the Equator and
variations in the natural noon cycles everywhere have the same
astronomical root based on the relationship between axial and orbital
motions.The reasoning of the NMM where rotational orientation has some
effect on Kepler's orbital geometry and the variable noon cycles
is ,to put it mildly,as childish as it gets.

The shared mechanism which causes no variations in daylight/darkness
at the Equator yet variations in the natural noon cycle there requires
the addition of an orbital component,one that is already observed by
looking at the orbital behavior of Uranus.

Just to remind you Mike,in the Piltdown Man episode,it was not the
people who were taken in by the hoax or those who built on the ideas
that became the most hated and despised ,it was those who knew it was
a hoax and kept it going out of personal convenience. even though it
had no productive legs.I am willing to concede that it is difficult to
extract the orbital component as a seperate motion with respect to the
central Sun whereas axial rotation occurs simultaneously as a seperate
motion thereby thew whole scheme becomes a modification of
heliocentric reasoning.The hoax comes in via the analemma where
variable inclination to the Sun was introduced despite the fact that
rotational orientation as a consequence of axial rotation keeps the
Earth pointing towards pOlaris throughout an annual orbit.

I do not know what it takes to shatter this sidereal monster and its
destructive effect on the noble Equation of Time scheme but it
requires genuine people who do not repeat old falsehoods as you have
just done.








  #9  
Old April 26th 08, 01:18 PM posted to uk.sci.astronomy
Pd
external usenet poster
 
Posts: 17
Default Equation of Time

oriel36 wrote:

a bunch of gibberish.

Who is this clueless dork? A troll? A scientologist?
A deranged astrologer? A nitwit necromancer?

--
Pd
  #10  
Old April 26th 08, 03:45 PM posted to uk.sci.astronomy
jim
external usenet poster
 
Posts: 27
Default Equation of Time

Pd wrote:

oriel36 wrote:

a bunch of gibberish.

Who is this clueless dork? A troll? A scientologist?
A deranged astrologer? A nitwit necromancer?


He's Gerald - a pompous, self important, deluded half-wit who believes
he's the only 'real' astronomer in this group.

Sort of the Chris Holland of uk.sci.astronomy and sci.astro.amateur but
without the blatent homophobia.

Jim
--
"Well, well. We've come a long way from the Prime Minister's
exploding cake." - Adam West, Batman.

Find me at http://www.UrsaMinorBeta.co.uk
 




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