Local Siderial Time?

"DaveC" wrote in message
al.net...
How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox, or
such. I
just want to know if a particular time in LST is fixed in relation to the
clock on the wall, or if it changes over the year, and how to calculate it
or
look it up.

Thanks,
You are really saying, "I don't want a definition", but "I want a
definition"...
A sidereal day, is four seconds shorter then the normal 'clock' day. So a
particular sidereal 'time' arrives four seconds earlier each day (when
compared to a normal clock).
Now the question of calculating it, depends on just how accurate you want to
go?. The simplest way (which is accurate enough for most uses), is to use a
chart, based on this 'drift' between the clocks. One is at:
http://pietro.org.tripod.com/Astro_U...ealVSCivil.htm
This is accurate enough for probably 98% of uses.
The formula to calculate the sidereal time is at:
http://www.space-plasma.qmul.ac.uk/h...rt/node10.html
and this is accurate enough for 99.9999% of applications.
Even this though, has a small amount of residual error.

Best Wishes

Roger Hamlett wrote:
"DaveC" wrote in message
al.net...
How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox,
or such. I just want to know if a particular time in LST is fixed in
relation to the clock on the wall, or if it changes over the year,
and how to calculate it or look it up.

Thanks,
You are really saying, "I don't want a definition", but "I want a
definition"...
A sidereal day, is four seconds shorter then the normal 'clock' day.
So a particular sidereal 'time' arrives four seconds earlier each day
(when compared to a normal clock).

Four minutes, surely? ;-)

Steve

--
www.frontierastro.co.uk

FrontierAstro - dedicated to Frontier and Astronomy

"Steve" wrote in message
news
Roger Hamlett wrote:
"DaveC" wrote in message
al.net...
How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox,
or such. I just want to know if a particular time in LST is fixed in
relation to the clock on the wall, or if it changes over the year,
and how to calculate it or look it up.

Thanks,
You are really saying, "I don't want a definition", but "I want a
definition"...
A sidereal day, is four seconds shorter then the normal 'clock' day.
So a particular sidereal 'time' arrives four seconds earlier each day
(when compared to a normal clock).

Four minutes, surely? ;-)

Steve
Sometimes they just pass like seconds... :-)
Dead right, a 'slip of the keyboard'.

Best Wishes

DaveC wrote in
al.net:

How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox, or
such. I just want to know if a particular time in LST is fixed in
relation to the clock on the wall, or if it changes over the year, and
how to calculate it or look it up.

Thanks,

Here are the principles.

Sidereal time is determined by the rotation of the earth with refernce to
the equinox. It takes 23h56m to make a 360 degree rotation.

Clock time based on a mean solar time and is the rotation of the earth with
refernce to a mean Sun. It is 24h00m and a 361 degree rotation.

Why 361 degrees?

Sun advances nearly 1 degree in the ecliptic every sidereal day.
Therefore the earth must rotate a further 1 degree or 4 minutes to catch up
to complete a solar day.

The sidereal clock thus gains 4 minutes accumulatively on a solar clock
every day.

The two clocks are by convention synchronized at 00h00m at the September
equinox. Thereafter they diverge by 4 minutes per day until they are 12
hours apart 6 months later at the March equinox. They contiune until they
once more synchronize at the following September equinox.

Martin Lewicki

At one day for fraction of a secont local time an ST are the same. At the
start of fall in Sept.

In message et, DaveC
writes

Is there a web site where I can enter Longitude and get a chart of LST?
Something done in Java, perhaps?

Thanks,

If you google on 'sidereal clock' you should find a nice little freeware
clock that you can download that reads your system clock and then
converts. I think one of the sites also has Java source code to download
as well.
Sorry I can't remember the domain but it should be pretty easy to find.
Denis
--
DT
Replace nospam with the antithesis of hills
*******************************************

On Wed, 17 Dec 2003 8:01:23 -0800, DaveC wrote:

On Wed, 17 Dec 2003 1:28:16 -0800, Roger Hamlett wrote
(in message ):


"DaveC" wrote in message
al.net...
How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox, or
such. I
just want to know if a particular time in LST is fixed in relation to the
clock on the wall, or if it changes over the year, and how to calculate it
or
look it up.

Thanks,
You are really saying, "I don't want a definition", but "I want a
definition"...
A sidereal day, is four seconds shorter then the normal 'clock' day. So a
particular sidereal 'time' arrives four seconds earlier each day (when
compared to a normal clock).
Now the question of calculating it, depends on just how accurate you want to
go?. The simplest way (which is accurate enough for most uses), is to use a
chart, based on this 'drift' between the clocks. One is at:
http://pietro.org.tripod.com/Astro_U...ealVSCivil.htm

Is there a web site where I can enter Longitude and get a chart of LST?
Something done in Java, perhaps?

Thanks,
http://www.jgiesen.de/astro/astroJS/...lock/index.htm
Good night!

Benoît Morrissette

Martin Lewicki wrote in message ...
DaveC wrote in
al.net:

How does LST correlate to our terrestrial time? I'm not looking for a
definition, or an explanation that includes angles of the equinox, or
such. I just want to know if a particular time in LST is fixed in
relation to the clock on the wall, or if it changes over the year, and
how to calculate it or look it up.

Thanks,

Here are the principles.

Sidereal time is determined by the rotation of the earth with refernce to
the equinox. It takes 23h56m to make a 360 degree rotation.


Thoroughly incorrect.

It is necessary to define a 24 hour day first before you determine
that the annual cycle is 365.25 days.

The basis for the 24 hour clock day relies on the axial rotation in 24
hours exactly and accurate clocks were developed by John Harrison on
that principle.

http://rubens.anu.edu.au/student.pro...aval/defin.htm



Clock time based on a mean solar time and is the rotation of the earth with
refernce to a mean Sun. It is 24h00m and a 361 degree rotation.


Thoroughly incorrect.

Nothing rotates more than 360 degrees and clocks maintain the 24
hour/360 degree equivalency for the axial rotation of the Earth.The
principles behind clocks for solving the longitude problem is that it
is noon along an entire longitude meridian at some location on the
planet.Because there is no observed equality from one axial rotation
to the next,brilliant men devised a computation known as the Equation
of Time to equalise the variation from one axial rotation to the next
or what amounts to the same thing,one 24 hour day to the next.


Why 361 degrees?

Sun advances nearly 1 degree in the ecliptic every sidereal day.
Therefore the earth must rotate a further 1 degree or 4 minutes to catch up
to complete a solar day.


By the sidereal method .986 deg or 3 min 56 seconds.

Because the true rotation rate is calculated as 24 hours = 360
degrees

1 deg = 4 min clock time

..986 deg = 3 min 56 sec clock time

24 hours minus 3 min 56 sec = 23 hours 56 min 04 sec.

http://www.absolutebeginnersastronomy.com/sidereal.gif

The catastrophic error is that you need to define a 24 hour clock
day first before you determine that there is 365 days 5 hours and 49
min in an annual cycle and all justifications for the sidereal value
begin on the wrong footing,the day is defined by the axial rotation of
the Earth via the Equation of Time and insofar as this reflects the 24
hour/360 degree equivalency.

Newton,in defining the difference between the natural unequal day and
the constant 24 hour clock day as the Equation of Time or the
difference between absolute time and relative time may have
unwittingly paved the way for tampering with the original
determination of the day linked to the isolation of the Earth's
rotation to 24 hours/360 degrees.

"Absolute time, in astronomy, is distinguished from relative, by the
equation or correlation of the vulgar time. For the natural days are
truly unequal, though they are commonly considered as equal and used
for a measure of time; astronomers correct this inequality for their
more accurate deducing of the celestial motions. It may be, that there
is no such thing as an equable motion, whereby time may be accurately
measured." Principia

http://members.tripod.com/~gravitee/definitions.htm

The price of tampering with the association between axial rotation
through 360 degrees and the 24 hour clock as Newton's absolute time is
that in the 21st century,men believe that the Earth has a constant
equable motion through 360 degrees and that motion is stellar
circumpolar motion.

Not even the creationist doctrine can compare to reasoning that links
the Earth's rotation directly to the sidereal value and stellar
circumpolar motion for ultimately it leads to the stellar circumpolar
framework.

http://home.t-online.de/home/sjkowollik/polaris.jpg

Now are you certain that the Earth's axial rotation through 360
degrees corresponds to the return of a reference star to the same
position in 23 hours 56 min 04 sec.








The sidereal clock thus gains 4 minutes accumulatively on a solar clock
every day.


The Equation of Time (EoT) contains positive and negative values of
minutes and seconds which were applied at observed noon to maintain
the transition from one 24 hour clock day to the next or one axial
rotation to the next.The EoT equalises the variation in a natural day
by treating axial rotation as constant and modifying the variation in
orbital motion due to Kepler's second law which generates the natural
inequality for each axial rotation.

Again,you cannot even to begin to define the sidereal value without
the 24 hour/360 degree equivalency but it appears that it does not
stop you from trying.



http://www.burnley.gov.uk/towneley/tryall/eot3.htm




The two clocks are by convention synchronized at 00h00m at the September
equinox. Thereafter they diverge by 4 minutes per day until they are 12
hours apart 6 months later at the March equinox. They contiune until they
once more synchronize at the following September equinox.

Martin Lewicki


Clocks and the longitude problem,the only means to sort all this out
and restore the Earth's axial rotation to the 24 hour/360 degree
equivalency.It does not matter that men got it badly wrong in 1905 by
tampering with the definition of a constant 24 hour day from the
natural unequal day via the EoT,it is a matter of appreceation.

"In default of better information we may without serious error (in
days of sail) take the recorded hour as in the apparent time of the
meridian of longitude mentioned in the account, and for form's sake
apply the equation of time to reduce to civil time of the meridian."

http://www.aandc.org/research/nautic..._and_date.html



I assure you that the Earth takes 24 hours to rotate 360 degrees on
its axis,that is the way it always was and will be.Ask anyone on the
street and they will tell you,they may not know the particulars of
defining a 24 hour day but it appears neither do you,no offense
intended.

Sidereal time is determined by the rotation of the earth with refernce to
the equinox. It takes 23h56m to make a 360 degree rotation.

Well, not quite, although if you mean referenced to a point on the celestial
sphere like the vernal or autumnal equinoxes, you would be right. Sidereal
time is determined by the rotation rate with respect to the stars. The Earth
rotates 360 degrees with respect to the stars in a period of 23 hrs, 56
minutes, 4.092 seconds. We generally say that local sidereal time is the
right ascension of the local meridian (or the hour-angle of the vernal
equinox). Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

(Oriel36) wrote in
om:

Martin Lewicki wrote in message
...
DaveC wrote in
al.net:

How does LST correlate to our terrestrial time? I'm not looking for
a definition, or an explanation that includes angles of the
equinox, or such. I just want to know if a particular time in LST
is fixed in relation to the clock on the wall, or if it changes
over the year, and how to calculate it or look it up.

Thanks,

Here are the principles.

Sidereal time is determined by the rotation of the earth with
refernce to the equinox. It takes 23h56m to make a 360 degree
rotation.


Thoroughly incorrect.

It is necessary to define a 24 hour day first before you determine
that the annual cycle is 365.25 days.

The basis for the 24 hour clock day relies on the axial rotation in 24
hours exactly and accurate clocks were developed by John Harrison on
that principle.

http://rubens.anu.edu.au/student.pro...aval/defin.htm

Agreed, in a mean solar day the earth rotates through 360 *degrees of
longitude*, but rotates nearly 361 degrees in space, ie in reference to a
fixed star on the celestial sphere.


Clock time based on a mean solar time and is the rotation of the
earth with refernce to a mean Sun. It is 24h00m and a 361 degree
rotation.


Thoroughly incorrect.

Nothing rotates more than 360 degrees and clocks maintain the 24
hour/360 degree equivalency for the axial rotation of the Earth.The
principles behind clocks for solving the longitude problem is that it
is noon along an entire longitude meridian at some location on the
planet.

It follows by your argument the moon does not rotate because it maintains
same face to earth.

Because there is no observed equality from one axial rotation
to the next,brilliant men devised a computation known as the Equation
of Time to equalise the variation from one axial rotation to the next
or what amounts to the same thing,one 24 hour day to the next.

Fair enough but equation of time is not relevant to the principles of this
argument.


Why 361 degrees?

Sun advances nearly 1 degree in the ecliptic every sidereal day.
Therefore the earth must rotate a further 1 degree or 4 minutes to
catch up to complete a solar day.


By the sidereal method .986 deg or 3 min 56 seconds.

Because the true rotation rate is calculated as 24 hours = 360
degrees

....of longitude on the earth's surface (or 361 deg in space).

1 deg = 4 min clock time

.986 deg = 3 min 56 sec clock time

24 hours minus 3 min 56 sec = 23 hours 56 min 04 sec.

http://www.absolutebeginnersastronomy.com/sidereal.gif

The catastrophic error is that you need to define a 24 hour clock
day first before you determine that there is 365 days 5 hours and 49
min in an annual cycle and all justifications for the sidereal value
begin on the wrong footing,the day is defined by the axial rotation of
the Earth via the Equation of Time and insofar as this reflects the 24
hour/360 degree equivalency.

Newton,in defining the difference between the natural unequal day and
the constant 24 hour clock day as the Equation of Time or the
difference between absolute time and relative time may have
unwittingly paved the way for tampering with the original
determination of the day linked to the isolation of the Earth's
rotation to 24 hours/360 degrees.

"Absolute time, in astronomy, is distinguished from relative, by the
equation or correlation of the vulgar time. For the natural days are
truly unequal, though they are commonly considered as equal and used
for a measure of time; astronomers correct this inequality for their
more accurate deducing of the celestial motions. It may be, that there
is no such thing as an equable motion, whereby time may be accurately
measured." Principia

http://members.tripod.com/~gravitee/definitions.htm

The price of tampering with the association between axial rotation
through 360 degrees and the 24 hour clock as Newton's absolute time is
that in the 21st century,men believe that the Earth has a constant
equable motion through 360 degrees and that motion is stellar
circumpolar motion.

Not even the creationist doctrine can compare to reasoning that links
the Earth's rotation directly to the sidereal value and stellar
circumpolar motion for ultimately it leads to the stellar circumpolar
framework.

http://home.t-online.de/home/sjkowollik/polaris.jpg

Now are you certain that the Earth's axial rotation through 360
degrees corresponds to the return of a reference star to the same
position in 23 hours 56 min 04 sec.








The sidereal clock thus gains 4 minutes accumulatively on a solar
clock every day.


The Equation of Time (EoT) contains positive and negative values of
minutes and seconds which were applied at observed noon to maintain
the transition from one 24 hour clock day to the next or one axial
rotation to the next.The EoT equalises the variation in a natural day
by treating axial rotation as constant and modifying the variation in
orbital motion due to Kepler's second law which generates the natural
inequality for each axial rotation.

Again,you cannot even to begin to define the sidereal value without
the 24 hour/360 degree equivalency but it appears that it does not
stop you from trying.



http://www.burnley.gov.uk/towneley/tryall/eot3.htm




The two clocks are by convention synchronized at 00h00m at the
September equinox. Thereafter they diverge by 4 minutes per day until
they are 12 hours apart 6 months later at the March equinox. They
contiune until they once more synchronize at the following September
equinox.

Martin Lewicki


Clocks and the longitude problem,the only means to sort all this out
and restore the Earth's axial rotation to the 24 hour/360 degree
equivalency.It does not matter that men got it badly wrong in 1905 by
tampering with the definition of a constant 24 hour day from the
natural unequal day via the EoT,it is a matter of appreceation.

"In default of better information we may without serious error (in
days of sail) take the recorded hour as in the apparent time of the
meridian of longitude mentioned in the account, and for form's sake
apply the equation of time to reduce to civil time of the meridian."

http://www.aandc.org/research/nautic..._and_date.html



I assure you that the Earth takes 24 hours to rotate 360 degrees

....of longitude

on
its axis,that is the way it always was and will be.Ask anyone on the
street and they will tell you,they may not know the particulars of
defining a 24 hour day but it appears neither do you,no offense
intended.

Offense not taken. Seems definitions are a matter of relative perspective
:-)

Martin