Once again, you're proving you've never actually taken a noon sight. By
claiming its just the same as a sunset you demonstrate your ignorance. At
sunset, the Sun is moving at its fastest apparent velocity - it's dropping at
over 10 arc-seconds per second, about one arc-minute every 5 seconds. At local
noon, its "hanging" near its highest point, varying less than one arc second for
almost two minutes. Anyone that has plotted even one noon sight knows this.
Even if you had one arc-second accuracy, you could still be off 30 miles, In
fact, your accuracy is about 100 times worse than that.

The only way to get an even approximate longitude with a noon sight is to take
many sights, and plot a curve. Ten minutes would not be a long enough time -
maybe 30 minutes would give you a lone enough time span.

Your claim that the "sun only stays at it's azimuth for one second" is
meaningless. There may be only an instant as the sun makes its meridian
passage, but determining this point can't be done as you suggest.

But you don't have to take my word for it - even though I worked as an
astronomer for 6 years, programming celestial navigation for a $250,000,000
spacecraft. I admit shipboard navigation is a bit different. Perhaps someone
else can arbitrate.



"Simple Simon" wrote in message
...

"Jeff Morris" wrote in message
...
Once again Neal has blown a chance to impress. If he had made a reasonable
claim, it might have been believable. But by claiming the impossible, he
proves
that he really knows nothing of celestial.

comments interspersed ...

"Simple Simon" wrote in message
...
One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local noon"
unless
you already know your longitude. If Neal had actually ever taken a Noon
Sight,
he would know this!

Hey, dummy! Celestial is based heavily on dead reckoning. Longitude can
be pretty closely gleaned by dead reckoning using only one noon sight
per day. The more accurate your dead reckoning the less time you have
to sit on the house bringing old sol down to the horizon and checking if
your angle is getting larger (patience), has stabilized (fix) or is getting
smaller (you missed it) Local noon is local noon is local noon. One needs
only an accurate watch to time when the sun is at noon. The tables then
tell you your longitude when this angle and time occurs and the offset
from GMT. It seems to me that YOU are the one lacking in working
knowledge of noon sights.



Poor Ole Thom who claims to have used a sextant seems to
not understand this simple fact.

1) the angle of the sun at local noon gives you your latitude.

2) the time differential of the sun's azimuth from Greenwich
mean time gives you the longitude.

True, but its a very tedious process for even an approximate position. It
can't
be done with "one sight."

Yes it can. That's the beauty of the noon sight. One sight does it all.


Expensive chronographs are no longer necessary.

This has been true for almost a century.

GPS time is plenty accurate enough

Well, duh!

as well as a good quartz watch set to radio signals from WWV.

Even a cheap quartz watch will do.


I can take one noon sight anywhere in the world covered by the
tables I have on board, correct it for errors and come up with
my position within ten miles easily every time provided it is not
overcast, raining or some such.

Nonsense. The "zenith distance" of the Sun varies less than one second for
almost two minutes at local noon. During this time the Earth moves about 30
miles at the Equator. And that's with one second accuracy! One minute
accuracy is considered pretty good - that might leave you 100 miles away.
Celestaire says Neal's plastic sextant typically has a 5 minute error.

And Neal is claiming he can do this with one sight! While it is possible to
do
this for latitude, it is completely impossible for longitude.

You are completely wrong. One accurate local noon angle of the sun
is ALL that's needed. The sun only stays at it's azimuth for one second.
A sight can be taken with a one or two second accuracy which is good
enough to place one in the ten-mile range which is all a sailor of a small
sailboat really needs.

Look at a sunset sometime. Tell me you cannot mark the exact second
the bottom limb touches the horizon. I can so you should be able to.
I don't know about your sextant buy mine allows me to create a sunset
at noon as I adjust the vernier. It is easy to tell when the sun touches
the horizon and then goes the other way. PUTZ! I can tell you are one
of these arrogant people who wish to muddle up the ease of a noon
sight so you can claim you do something magic with your sextant. It
simply ain't so. Any old fool can take a noon sight and ascertain their
position with great accuracy.

S.Simon

You're totally stupid. The fact is the Sun moves across the sky
at the very same speed all the time it moves across the sky.

Are you so stupid that you actually think the Sun speeds
up as it nears the horizon? Bwahahahahahahhahahaha!

S.Simon



"Jeff Morris" wrote in message ...
Once again, you're proving you've never actually taken a noon sight. By
claiming its just the same as a sunset you demonstrate your ignorance. At
sunset, the Sun is moving at its fastest apparent velocity - it's dropping at
over 10 arc-seconds per second, about one arc-minute every 5 seconds. At local
noon, its "hanging" near its highest point, varying less than one arc second for
almost two minutes. Anyone that has plotted even one noon sight knows this.
Even if you had one arc-second accuracy, you could still be off 30 miles, In
fact, your accuracy is about 100 times worse than that.

The only way to get an even approximate longitude with a noon sight is to take
many sights, and plot a curve. Ten minutes would not be a long enough time -
maybe 30 minutes would give you a lone enough time span.

Your claim that the "sun only stays at it's azimuth for one second" is
meaningless. There may be only an instant as the sun makes its meridian
passage, but determining this point can't be done as you suggest.

But you don't have to take my word for it - even though I worked as an
astronomer for 6 years, programming celestial navigation for a $250,000,000
spacecraft. I admit shipboard navigation is a bit different. Perhaps someone
else can arbitrate.



"Simple Simon" wrote in message
...

"Jeff Morris" wrote in message
...
Once again Neal has blown a chance to impress. If he had made a reasonable
claim, it might have been believable. But by claiming the impossible, he
proves
that he really knows nothing of celestial.

comments interspersed ...

"Simple Simon" wrote in message
...
One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local noon"
unless
you already know your longitude. If Neal had actually ever taken a Noon
Sight,
he would know this!

Hey, dummy! Celestial is based heavily on dead reckoning. Longitude can
be pretty closely gleaned by dead reckoning using only one noon sight
per day. The more accurate your dead reckoning the less time you have
to sit on the house bringing old sol down to the horizon and checking if
your angle is getting larger (patience), has stabilized (fix) or is getting
smaller (you missed it) Local noon is local noon is local noon. One needs
only an accurate watch to time when the sun is at noon. The tables then
tell you your longitude when this angle and time occurs and the offset
from GMT. It seems to me that YOU are the one lacking in working
knowledge of noon sights.



Poor Ole Thom who claims to have used a sextant seems to
not understand this simple fact.

1) the angle of the sun at local noon gives you your latitude.

2) the time differential of the sun's azimuth from Greenwich
mean time gives you the longitude.

True, but its a very tedious process for even an approximate position. It
can't
be done with "one sight."

Yes it can. That's the beauty of the noon sight. One sight does it all.


Expensive chronographs are no longer necessary.

This has been true for almost a century.

GPS time is plenty accurate enough

Well, duh!

as well as a good quartz watch set to radio signals from WWV.

Even a cheap quartz watch will do.


I can take one noon sight anywhere in the world covered by the
tables I have on board, correct it for errors and come up with
my position within ten miles easily every time provided it is not
overcast, raining or some such.

Nonsense. The "zenith distance" of the Sun varies less than one second for
almost two minutes at local noon. During this time the Earth moves about 30
miles at the Equator. And that's with one second accuracy! One minute
accuracy is considered pretty good - that might leave you 100 miles away.
Celestaire says Neal's plastic sextant typically has a 5 minute error.

And Neal is claiming he can do this with one sight! While it is possible to
do
this for latitude, it is completely impossible for longitude.

You are completely wrong. One accurate local noon angle of the sun
is ALL that's needed. The sun only stays at it's azimuth for one second.
A sight can be taken with a one or two second accuracy which is good
enough to place one in the ten-mile range which is all a sailor of a small
sailboat really needs.

Look at a sunset sometime. Tell me you cannot mark the exact second
the bottom limb touches the horizon. I can so you should be able to.
I don't know about your sextant buy mine allows me to create a sunset
at noon as I adjust the vernier. It is easy to tell when the sun touches
the horizon and then goes the other way. PUTZ! I can tell you are one
of these arrogant people who wish to muddle up the ease of a noon
sight so you can claim you do something magic with your sextant. It
simply ain't so. Any old fool can take a noon sight and ascertain their
position with great accuracy.

S.Simon

That's why I said "apparent velocity." As I said, the apparent velocity
changes dramatically, from being very fast near the horizon, to hanging almost
motionless at noon. Basic stuff, but its enough to prove that you've never done
a noon sight.

See my response to Wally - it has the reference from Bowditch. But its pretty
clear you have no desire to actually learn this stuff; you thought nobody would
call your bluff.



"Simple Simon" wrote in message
news
You're totally stupid. The fact is the Sun moves across the sky
at the very same speed all the time it moves across the sky.

Are you so stupid that you actually think the Sun speeds
up as it nears the horizon? Bwahahahahahahhahahaha!

S.Simon



"Jeff Morris" wrote in message
...
Once again, you're proving you've never actually taken a noon sight. By
claiming its just the same as a sunset you demonstrate your ignorance. At
sunset, the Sun is moving at its fastest apparent velocity - it's dropping
at
over 10 arc-seconds per second, about one arc-minute every 5 seconds. At
local
noon, its "hanging" near its highest point, varying less than one arc second
for
almost two minutes. Anyone that has plotted even one noon sight knows
this.
Even if you had one arc-second accuracy, you could still be off 30 miles,
In
fact, your accuracy is about 100 times worse than that.

The only way to get an even approximate longitude with a noon sight is to
take
many sights, and plot a curve. Ten minutes would not be a long enough
time -
maybe 30 minutes would give you a lone enough time span.

Your claim that the "sun only stays at it's azimuth for one second" is
meaningless. There may be only an instant as the sun makes its meridian
passage, but determining this point can't be done as you suggest.

But you don't have to take my word for it - even though I worked as an
astronomer for 6 years, programming celestial navigation for a $250,000,000
spacecraft. I admit shipboard navigation is a bit different. Perhaps
someone
else can arbitrate.



"Simple Simon" wrote in message
...

"Jeff Morris" wrote in message
...
Once again Neal has blown a chance to impress. If he had made a
reasonable
claim, it might have been believable. But by claiming the impossible,
he
proves
that he really knows nothing of celestial.

comments interspersed ...

"Simple Simon" wrote in message
...
One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local
noon"
unless
you already know your longitude. If Neal had actually ever taken a Noon
Sight,
he would know this!

Hey, dummy! Celestial is based heavily on dead reckoning. Longitude can
be pretty closely gleaned by dead reckoning using only one noon sight
per day. The more accurate your dead reckoning the less time you have
to sit on the house bringing old sol down to the horizon and checking if
your angle is getting larger (patience), has stabilized (fix) or is
getting
smaller (you missed it) Local noon is local noon is local noon. One needs
only an accurate watch to time when the sun is at noon. The tables then
tell you your longitude when this angle and time occurs and the offset
from GMT. It seems to me that YOU are the one lacking in working
knowledge of noon sights.



Poor Ole Thom who claims to have used a sextant seems to
not understand this simple fact.

1) the angle of the sun at local noon gives you your latitude.

2) the time differential of the sun's azimuth from Greenwich
mean time gives you the longitude.

True, but its a very tedious process for even an approximate position.
It
can't
be done with "one sight."

Yes it can. That's the beauty of the noon sight. One sight does it all.


Expensive chronographs are no longer necessary.

This has been true for almost a century.

GPS time is plenty accurate enough

Well, duh!

as well as a good quartz watch set to radio signals from WWV.

Even a cheap quartz watch will do.


I can take one noon sight anywhere in the world covered by the
tables I have on board, correct it for errors and come up with
my position within ten miles easily every time provided it is not
overcast, raining or some such.

Nonsense. The "zenith distance" of the Sun varies less than one second
for
almost two minutes at local noon. During this time the Earth moves
about 30
miles at the Equator. And that's with one second accuracy! One minute
accuracy is considered pretty good - that might leave you 100 miles
away.
Celestaire says Neal's plastic sextant typically has a 5 minute error.

And Neal is claiming he can do this with one sight! While it is
possible to
do
this for latitude, it is completely impossible for longitude.

You are completely wrong. One accurate local noon angle of the sun
is ALL that's needed. The sun only stays at it's azimuth for one second.
A sight can be taken with a one or two second accuracy which is good
enough to place one in the ten-mile range which is all a sailor of a small
sailboat really needs.

Look at a sunset sometime. Tell me you cannot mark the exact second
the bottom limb touches the horizon. I can so you should be able to.
I don't know about your sextant buy mine allows me to create a sunset
at noon as I adjust the vernier. It is easy to tell when the sun touches
the horizon and then goes the other way. PUTZ! I can tell you are one
of these arrogant people who wish to muddle up the ease of a noon
sight so you can claim you do something magic with your sextant. It
simply ain't so. Any old fool can take a noon sight and ascertain their
position with great accuracy.

S.Simon

Jeff Morris wrote:

One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local
noon" unless you already know your longitude. If Neal had actually
ever taken a Noon Sight, he would know this!

I am but a sweet, innocent, fresh-faced n00b, and wonder if my reasoning is
correct...

I have a sextant and an accurate chronometer set to GMT. I am somewhere on
the surface of the earth, but know not where. I awaken from my slumbers one
morning and find myself wondering what my longitude is, so I watch the sun's
upward climb across the sky. As it approaches zenith - local noon - I note
the time on my chronometer and then crunch time into degrees to determine my
longitude.


--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)

That's it but you need tables. You need tables because you measure
zenith and local hour angle.

S.Simon


"Wally" wrote in message ...
Jeff Morris wrote:

One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local
noon" unless you already know your longitude. If Neal had actually
ever taken a Noon Sight, he would know this!

I am but a sweet, innocent, fresh-faced n00b, and wonder if my reasoning is
correct...

I have a sextant and an accurate chronometer set to GMT. I am somewhere on
the surface of the earth, but know not where. I awaken from my slumbers one
morning and find myself wondering what my longitude is, so I watch the sun's
upward climb across the sky. As it approaches zenith - local noon - I note
the time on my chronometer and then crunch time into degrees to determine my
longitude.


--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)

Pleas explain which "tables" you are talking about and what
calculations you are making for sextant altitude and time. You sure you
want LHA?

otn

Simple Simon wrote:
That's it but you need tables. You need tables because you measure
zenith and local hour angle.

S.Simon

Sight Reduction Tables of course. I use HO249 for speed and simplicity.

You must have local hour angle because the sight is always a combination
of local hour angle and zenith. The tables help you to turn the local hour
angle into latitude since the sun moves daily because of the tilt of the
earth as the seasons progress.

S.Simon



"otnmbrd" wrote in message ink.net...
Pleas explain which "tables" you are talking about and what
calculations you are making for sextant altitude and time. You sure you
want LHA?

otn

Simple Simon wrote:
That's it but you need tables. You need tables because you measure
zenith and local hour angle.

S.Simon

Simple Simon wrote:
That's it but you need tables. You need tables because you measure
zenith and local hour angle.

To find longitude? If so, how's that done? I just put together a little
spreadsheet which seems to find longitude for zenith at any given GMT time.

06:00 gives -90 (90 deg east)
18:00 gives 90W
17:21:50 puts me very close to your meridian - 80d 27.5'W


--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)

Yes, its just that simple. You understand perfectly. There's only one problem.
Here's what Bowditch has to say, from the 2002 edition (LAN is Local Apparent
Noon):

Determining the time of meridian passage presents a
problem because the Sun appears to hang for a finite time
at its local maximum altitude. Therefore, noting the time
of maximum sextant altitude is not sufficient for
determining the precise time of LAN. Two methods are
available to obtain LAN with a precision sufficient for
determining longitude: (1) the graphical method and (2)
the calculation method. The graphical method is
discussed first below.
See Figure 2011. For about 30 minutes before the
estimated time of LAN, measure and record several sextant
altitudes and their corresponding times. Continue taking
sights for about 30 minutes after the Sun has descended
from the maximum recorded altitude. Increase the sighting
frequency near the meridian passage. One sight every 20-30
seconds should yield good results near meridian passage;
less frequent sights are required before and after.

Bowditch goes on to describe the process of plotting the curve and estimating
the time. The other approach is similar, except they give a more mathematical
method for averaging all the sights. Either way relies on taking a number of
sights before and after the Meridian Passage.

The exercise of plotting a Noon Sight is one of the first things a novice
learns. Neal's lack of understanding shows he has never actually done this.

Reference section 2011
http://pollux.nss.nima.mil/NAV_PUBS/APN/Chapt-20.pdf


"Wally" wrote in message
...
Jeff Morris wrote:

One sight at local noon yields your latitude and longitude.

Clearly not true - for starters, you can't take "one sight at local
noon" unless you already know your longitude. If Neal had actually
ever taken a Noon Sight, he would know this!

I am but a sweet, innocent, fresh-faced n00b, and wonder if my reasoning is
correct...

I have a sextant and an accurate chronometer set to GMT. I am somewhere on
the surface of the earth, but know not where. I awaken from my slumbers one
morning and find myself wondering what my longitude is, so I watch the sun's
upward climb across the sky. As it approaches zenith - local noon - I note
the time on my chronometer and then crunch time into degrees to determine my
longitude.


--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)

Jeff Morris wrote:
Yes, its just that simple. You understand perfectly.

Good-o.


There's only
one problem. Here's what Bowditch has to say, from the 2002 edition
(LAN is Local Apparent Noon):

snip

Yup, I'm aware of the difficulty in taking a sight precisely at local noon
due to the sun apparently hanging in the sky, and that some method of
extrapolation from sights either side of zenith is needed.


The exercise of plotting a Noon Sight is one of the first things a
novice learns. Neal's lack of understanding shows he has never
actually done this.

Neal seems to be contending that it's possible to line up a limb of the sun
with the horizon, such that there's a perceptible difference between limb
and horizon being 'in contact' and being separated. While this may well be
possible when everything is nice and stable, I can't help feeling that it
would be rather difficult in a bobbing boat.


--
Wally
www.art-gallery.myby.co.uk
Latest work: The Langlois Bridge (after Van Gogh)