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Main
Date: 23 Sep 2006 09:21:31
From: canopus56
Subject: Happy equinox to all
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Began Sept 23 04:03 UTC
- Canopus56
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Date: 23 Sep 2006 19:28:24
From: canopus56
Subject: Re: Happy equinox to all
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canopus56 wrote:
> autumnal equinox that occurs when the Sun reaches ecliptic longitude
> 270 degrees
Should read 180 ecliptic degrees, not 270 degrees. - C
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Date: 24 Sep 2006 01:54:19
From: Jim Klein
Subject: Re: Happy equinox to all
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"canopus56" <canopus56@yahoo.com > wrote:
>Began Sept 23 04:03 UTC
>
>- Canopus56
Since they outlawed human sacrifice, equinoxes have been kind of drab
and even if they had not, virgin humans are a bitch to find.
James E. Klein
jameseklein@earthlink.net
Engineering Calculations
http://www.ecalculations.com
ecalculations@ecalculations.com
Engineering Calculations is the home of
the KDP-2 Optical Design Program
for Windows and (soon) MAC OSX
Free KDP-2 (DEMO) downloadable!
1-818-507-5706 (Voice and Fax)
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Date: 23 Sep 2006 18:41:58
From: canopus56
Subject: Re: Happy equinox to all
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Florian wrote:
> Well, to quibble, equinoxes are an instant in time. They don't really begin/end. But fall began in the north and spring in the south! Happy equinox Canopus56!! ;-)
True enough, you have to make a distinction between astronomical
autumnal equinox that occurs when the Sun reaches ecliptic longitude
270 degrees and the local "civil" equinoxes that occur at local noon
for the following 24 hours.
Autumnal equinox - Sundial gnomons only trace a straight line between
10 and 4 on equinoxes, here animated between Sept. 23, 2006 between
12:24MDT and 2:01MDT
http://www.utahastronomy.com/view_photo.php?set_albumName=album40&id=20060923SDialAnimate
(234kb)
in
http://www.utahastronomy.com/view_album.php?set_albumName=kurt
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Date: 24 Sep 2006 11:42:33
From: Paul Schlyter
Subject: Re: Happy equinox to all
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In article <1159062118.140624.74270@k70g2000cwa.googlegroups.com >,
canopus56 <canopus56@yahoo.com > wrote:
> Florian wrote:
>> Well, to quibble, equinoxes are an instant in time. They don't really begin/end. But fall began in the north and spring in the south! Happy equinox Canopus56!! ;-)
>
> True enough, you have to make a distinction between astronomical
> autumnal equinox that occurs when the Sun reaches ecliptic longitude
> 270 degrees and the local "civil" equinoxes that occur at local noon
> for the following 24 hours.
??????????????????????????
I've never ever heard of any "local civil" equinox defined differently
than the astronomical definition. Could you provide any references?
It's quite common to just give the date and not the time-of-day of the
equinox though. But that doesn't mean that the equinox is claimed to
happen precisely at local noon.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 24 Sep 2006 19:03:22
From: Florian
Subject: Re: Happy equinox to all
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In Australia spring began on Sept 1st. Autumn begins on March 1st, =
summer on December 1st, winter on June 1st. I don't know why they don't =
follow the actual equnoxes/solstices.=20
.Florian
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Date: 23 Sep 2006 22:20:01
From: Florian
Subject: Re: Happy equinox to all
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>Began Sept 23 04:03 UTC
Well, to quibble, equinoxes are an instant in time. They don't really =
begin/end. But fall began in the north and spring in the south! Happy =
equinox Canopus56!! ;-)
.Florian
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Date: 24 Sep 2006 16:27:22
From: canopus56
Subject: Re: Happy equinox to all
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Paul Schlyter wrote:
> I've never ever heard of any "local civil" equinox defined differently
> than the astronomical definition. Could you provide any references?
"Local apparent equinox" would be a better usage. "Civil equinox"
implies governmental recognition that is does not exist. That's for
catching the discrepancy and imprecise use of terms.
> Could you provide any references?
None that are authoritative. It is common general public usage, in my
experience. Few, if any, general public members I have discussed the
equinoxes and solstices with are aware of the precise astronomical
equinoxes or solstices based on an instant of ecliptic longitude. Most
think of the solstices and equinoxes in terms of local apparent
position of the Sun - probably a residual effect of the use sundials
for 1,700 years. On my local tv news for the past 30 years, the time of
equinox is usually reported as the local apparent and not the
astronomical equinox. Over the years, it has been reported both ways
in local newspapers. This seems particularly true of the winter
solstice, which is more often than not reported by the press based on
the time of local apparent solstice, not the astrometric winter
solstice.
Thanks, Canopus56
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Date: 25 Sep 2006 07:13:28
From: Paul Schlyter
Subject: Re: Happy equinox to all
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In article <1159140442.298117.218470@m73g2000cwd.googlegroups.com >,
canopus56 <canopus56@yahoo.com > wrote:
> Paul Schlyter wrote:
>> I've never ever heard of any "local civil" equinox defined differently
>> than the astronomical definition. Could you provide any references?
>
> "Local apparent equinox" would be a better usage. "Civil equinox"
> implies governmental recognition that is does not exist. That's for
> catching the discrepancy and imprecise use of terms.
>
>> Could you provide any references?
>
> None that are authoritative. It is common general public usage, in my
> experience. Few, if any, general public members I have discussed the
> equinoxes and solstices with are aware of the precise astronomical
> equinoxes or solstices based on an instant of ecliptic longitude. Most
> think of the solstices and equinoxes in terms of local apparent
> position of the Sun - probably a residual effect of the use sundials
> for 1,700 years. On my local tv news for the past 30 years, the time of
> equinox is usually reported as the local apparent and not the
> astronomical equinox. Over the years, it has been reported both ways
> in local newspapers. This seems particularly true of the winter
> solstice, which is more often than not reported by the press based on
> the time of local apparent solstice, not the astrometric winter
> solstice.
>
> Thanks, Canopus56
As a matter of fact, the time for the equinox, as published in the
astronomical ephemerides, is based on the Sun's (geocentric) apparent
position, not its astrometric position. If the true position had been
used instead of the apparent position, the time of the equinox would be
8 minutes earlier - the difference is due to the light-time from the
Sun to the Earth.
You use the phrase "local apparent position of the Sun", which
(astronomically) ought to mean the apparent topocentric position of
the Sun. Using the topocentric instead of the geocentric position
would yield a time for the equinox which would differ by up to some 4
minutes (the time it takes for the Earth to, in its orbit, travel a
distance equal to its own radius), depending on which position on the
Earth you used for computing your topocentric position.
Using astrometric positions for the Sun would yield greater
differences. How much depends on which epoch you choose for your
astrometric position: if you choose an epoch of the time of Ancient
Greece, for instance, the "equinox" would happen about one month
later! But using astrometric positions of the Sun to define the
equinox would be pointless - you do want to know when the Sun crosses
the celestial equator in the sky where it resides today - not where it
resided a number of years ago......
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 24 Sep 2006 12:35:14
From: oriel36
Subject: Re: Happy equinox to all
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canopus56 wrote:
> Florian wrote:
> > Well, to quibble, equinoxes are an instant in time. They don't really begin/end. But fall began in the north and spring in the south! Happy equinox Canopus56!! ;-)
>
> True enough, you have to make a distinction between astronomical
> autumnal equinox that occurs when the Sun reaches ecliptic longitude
> 270 degrees and the local "civil" equinoxes that occur at local noon
> for the following 24 hours.
>
I like your misplaced geocentric courage and good for you.
The Earth did not tilt towards the Sun today to cause the Equinox,the
change in orbital orientation of the Earth split the poles in two. As
the polar axis is determined by terrestial rotation you can enjoy the
Equinox event as a local effect between axial and orbital orientations
but be sure to gauge what is moving and what is not.
> Autumnal equinox - Sundial gnomons only trace a straight line between
> 10 and 4 on equinoxes, here animated between Sept. 23, 2006 between
> 12:24MDT and 2:01MDT
>
> http://www.utahastronomy.com/view_photo.php?set_albumName=album40&id=20060923SDialAnimate
> (234kb)
>
> in
>
> http://www.utahastronomy.com/view_album.php?set_albumName=kurt
This business of tracing the arc of a shadow as an accurate
representation of axial and orbital motion has to cease.The
determination of local noon due to the rotation of the Earth occurs on
the same line with each rotation (no such things as an analemma).the
variation in lengths of the shadow at that moment represent the orbital
orientation of the Earth and certainly not the 'tilt' of the Earth.
There is really no big deal with determining that the return of a
shadow to local noon has nothing to do with the arc of a shadow but
rather the pace of the shadow back to noon representing the total
length of a day.The change in this pace is due to Keplerian orbital
geometry and the changing rate of orbital orientation.
Pity I cannot discuss this with somebody as courageous as you.
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Date: 25 Sep 2006 14:08:39
From: laura halliday
Subject: Re: Happy equinox to all
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canopus56 wrote:
> Began Sept 23 04:03 UTC
>
> - Canopus56
To commemorate the occasion I cobbled together a little
program that implements the algorithm in Chapter 27 of
Astronomical Algorithms by Meeus.
Some day I will do it the "proper" way with VSOP87, but
for now the simplified algorithm will do. I used my own
algorithm to turn Julian dates into calendar dates.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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Date: 25 Sep 2006 10:40:09
From: oriel36
Subject: Re: Happy equinox to all
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Paul Schlyter wrote:
> In article <1159140442.298117.218470@m73g2000cwd.googlegroups.com>,
> canopus56 <canopus56@yahoo.com> wrote:
>
> > Paul Schlyter wrote:
> >> I've never ever heard of any "local civil" equinox defined differently
> >> than the astronomical definition. Could you provide any references?
> >
> > "Local apparent equinox" would be a better usage. "Civil equinox"
> > implies governmental recognition that is does not exist. That's for
> > catching the discrepancy and imprecise use of terms.
> >
> >> Could you provide any references?
> >
> > None that are authoritative. It is common general public usage, in my
> > experience. Few, if any, general public members I have discussed the
> > equinoxes and solstices with are aware of the precise astronomical
> > equinoxes or solstices based on an instant of ecliptic longitude. Most
> > think of the solstices and equinoxes in terms of local apparent
> > position of the Sun - probably a residual effect of the use sundials
> > for 1,700 years. On my local tv news for the past 30 years, the time of
> > equinox is usually reported as the local apparent and not the
> > astronomical equinox. Over the years, it has been reported both ways
> > in local newspapers. This seems particularly true of the winter
> > solstice, which is more often than not reported by the press based on
> > the time of local apparent solstice, not the astrometric winter
> > solstice.
> >
> > Thanks, Canopus56
>
> As a matter of fact, the time for the equinox, as published in the
> astronomical ephemerides, is based on the Sun's (geocentric) apparent
> position, not its astrometric position. If the true position had been
> used instead of the apparent position, the time of the equinox would be
> 8 minutes earlier - the difference is due to the light-time from the
> Sun to the Earth.
>
> You use the phrase "local apparent position of the Sun", which
> (astronomically) ought to mean the apparent topocentric position of
> the Sun. Using the topocentric instead of the geocentric position
> would yield a time for the equinox which would differ by up to some 4
> minutes (the time it takes for the Earth to, in its orbit, travel a
> distance equal to its own radius), depending on which position on the
> Earth you used for computing your topocentric position.
>
> Using astrometric positions for the Sun would yield greater
> differences. How much depends on which epoch you choose for your
> astrometric position: if you choose an epoch of the time of Ancient
> Greece, for instance, the "equinox" would happen about one month
> later! But using astrometric positions of the Sun to define the
> equinox would be pointless - you do want to know when the Sun crosses
> the celestial equator in the sky where it resides today - not where it
> resided a number of years ago......
>
>
> --
> ----------------------------------------------------------------
> Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
> e-mail: pausch at stockholm dot bostream dot se
> WWW: http://stjarnhimlen.se/
At least Canopus has courage whereas you strive to be as obscure as
possible and finish with a vacuous question.
You tried the same thing years ago with the Equation of Time using a
variable axial tilting Earth to the Sun.
Perhaps you should explain to Canopus here how much the Earth tilted
towards the Sun today ?.
Don't bother,a little effort to appreciate that the Earth's orbital
motion as a seperate motion,treat the orbital orientation change
against axial orientation as a local event with local consequences and
above all drop this silly variable tilting Earth and have orbital
orientation split the polar axis at the Equinox.
Your kind have made a career out of making gorgeous things obscure and
ridiculous,my turn to present the outlines of something that can be
appreciated fairly easily.
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