In message 20120124115848.312d60bd4fccce4f3e71c136@kinali.ch, Attila Kinali w
rites:

Back then the stars were the coordinate system and the position of
the telescope the unknown, so you did it by observing stars with
documented coordinates with your new telescope and then you set
your clock and calculated your lattitude accordingly.

Remember: back then longitude and time were as single convolved coordinate.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On Tue, 24 Jan 2012 11:04:08 +0000
"Poul-Henning Kamp" phk@phk.freebsd.dk wrote:

That's what i'm aiming at. Yes, the lattitude can be calculated
using angle measurements relative to a known horizontal plane (mercury
mirror) or a vertical line (plumb bob). Still not easy to get below
an arc minute, but doable.

But how do you untangle longitude and time? How do you know that you
are looking exactly south (or north)?

		Attila Kinali

--
The trouble with you, Shev, is you don't say anything until you've saved
up a whole truckload of damned heavy brick arguments and then you dump
them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

In message 20120124121642.4a8ad1def54bc32cca92875c@kinali.ch, Attila Kinali w
rites:

North/South can be done by timing (widely spaced in inclination)
stellar transits relative to each other.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

On Tue, Jan 24, 2012 at 3:16 AM, Attila Kinali attila@kinali.ch wrote:

Sailingships and trade was what pushed this.  At the time of Columbus
he was able to know his latitude within a few 10s of miles but even
after returning to Europe he did no know how far around the world he
had sailed.  Was it 1/3rd or 2/3rds?  They had no way to know.    The
problem was that on one had a clock that should keep time well enough.
They used hour glasses on board ship for short duration time keeping
but those were of no use on a longer ocean crossing.

Later they discovered the idea of common view of the moons of Jupiter
and they could measure the time from local noon some even on Jupitor
while a person back home did the same thing.  Later when he got back
home they compare notes and then know the difference in longitude.
Good ocean going clocks were still centuries away.    But in the
1500's they could only know the location after the fact when they
returned

--

Chris Albertson
Redondo Beach, California

Yes, the first real push was the Longitude Act (1714) and the Harrison's
clocks.

On Tue, Jan 24, 2012 at 5:36 PM, Chris Albertson
albertson.chris@gmail.comwrote:

Maybe the Longitude Act was issued also because of the disaster occured in
1707 due to a navigation error: the Royal Navy fleet lost 4 of its 15 ships.

On Tue, Jan 24, 2012 at 5:50 PM, Azelio Boriani azelio.boriani@screen.itwrote:

If you're looking for a really interesting topic to read about, the
development of an accurate ship-board clock is really fascinating!  And it
wasn't done overnight!

Lee  K9WRU
----- Original Message -----
From: "Chris Albertson" albertson.chris@gmail.com
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Sent: Tuesday, January 24, 2012 10:36 AM
Subject: Re: [time-nuts] establishing your position w/o gps

I've read the book by Dava Sobel "Longitude"... not technical but
interesting for me.

On Tue, Jan 24, 2012 at 6:05 PM, Lee Mushel herbert3@centurytel.net wrote:

I think James Burke discussed these clocks in one of his documentary
series.  Besides not using a pendulum, they were temperature
compensated by using materials with opposite temperature coefficients
of expansion and then gimbaled for use on a rolling and pitching ship.

Oddly enough, the phase locked loop came significantly earlier when a
clock maker used it to regulate pendulum clocks overnight to quickly
calibrate a new clock to a reference clock.

On Tue, 24 Jan 2012 17:50:54 +0100, Azelio Boriani
azelio.boriani@screen.it wrote:

On Tue, 24 Jan 2012 11:05:58 -0600
"Lee Mushel" herbert3@centurytel.net wrote:

If you have a few references on books to read, you shouldn't keep them
for yourself ;-)

		Attila Kinali

--
Why does it take years to find the answers to
the questions one should have asked long ago?

If you want to try your hand at position determination in the pre
radio nav days you can buy a "studen sextent"  It's a low cost plastic
instrument sells for about $60.  Better ones start at $200 with $500
to $800 for a good one.  But it required much pratice and training to
outgrow the plastic instrument.    I took the class.    I think most
anyone who wants to sail on the ocean had better take the class just
in case their GPS fails.  I know some one who had both his primary
and backup GPSes fail and he was still a week from Hawaii.  They had
to revert to the old techniques from the 1700's

Much of pre-GPS position determination is not about finding your
latitude and longitude.  That is a modern notion.    What they did and
what sailors still do is find a "line of position".  That means "I am
some place on this line but I don't know where on the line"  There are
many ways to do this and they would work every method and find several
lines.  If they could see land they could shoot a compass bearing and
draw a reciprocal bearing and know they were on that line.  They would
know the ship's heading and could estimate drift and know course over
ground was parallel to that.  They could always find a latitude line.
Then if they did this right some of these lines would roughly
intersect and they would know the position without need to know
longitude.  There were other methods to find lines that required an
estimate of your speed and without clocks they resorted to chants and
songs (jo ho, jo ho,...)  As long as you sing the old pirate song at
the same tempo every time you have a decent clock.  Then you measure
distance by tossing a big chunk of lumber overboard with a measured
rope tied to it.  The captains hated doing math by hand so they
calibrated the rope by tieing knots at intervals so the natural unit
was one arc minute at the equator and called it a "knot".

My buddy who was headed to hawaii put both GPSes in the oven in the
galley and after three days was able to get one of them to work a few
minutes  a couple times a day.  That was enough.  But he said he was
within maybe 15 miles of where he thought he was

Basically your estimated course line intersected with a line of
latitude gives you longitude.

On Tue, Jan 24, 2012 at 8:50 AM, Azelio Boriani
azelio.boriani@screen.it wrote:

--

Chris Albertson
Redondo Beach, California

In addition to the moons of Jupiter, there was a method in direct
competition with Harrison. It was the Lunar distance method. The Lunar
distance method used the position of the Earth's moon against the zodiac as
a clock. The term lunar distance was used because the navigator measured the
angular distance from the moon to various stars to establish the moon's
position and then the time was deduced from lunar position tables.
Developing the lunar distance tables was part of the reason for establishing
the Royal Observatory.

John  WA4WDL

From: "Chris Albertson" albertson.chris@gmail.com
Sent: Tuesday, January 24, 2012 11:36 AM
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Subject: Re: [time-nuts] establishing your position w/o gps

Hi

If you spend some time on the auction sites you can find some fairly good
(though not brand name) sextants on the cheap.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chris Albertson
Sent: Tuesday, January 24, 2012 12:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] establishing your position w/o gps

If you want to try your hand at position determination in the pre
radio nav days you can buy a "studen sextent"  It's a low cost plastic
instrument sells for about $60.  Better ones start at $200 with $500
to $800 for a good one.  But it required much pratice and training to
outgrow the plastic instrument.    I took the class.    I think most
anyone who wants to sail on the ocean had better take the class just
in case their GPS fails.  I know some one who had both his primary
and backup GPSes fail and he was still a week from Hawaii.  They had
to revert to the old techniques from the 1700's

Much of pre-GPS position determination is not about finding your
latitude and longitude.  That is a modern notion.    What they did and
what sailors still do is find a "line of position".  That means "I am
some place on this line but I don't know where on the line"  There are
many ways to do this and they would work every method and find several
lines.  If they could see land they could shoot a compass bearing and
draw a reciprocal bearing and know they were on that line.  They would
know the ship's heading and could estimate drift and know course over
ground was parallel to that.  They could always find a latitude line.
Then if they did this right some of these lines would roughly
intersect and they would know the position without need to know
longitude.  There were other methods to find lines that required an
estimate of your speed and without clocks they resorted to chants and
songs (jo ho, jo ho,...)  As long as you sing the old pirate song at
the same tempo every time you have a decent clock.  Then you measure
distance by tossing a big chunk of lumber overboard with a measured
rope tied to it.  The captains hated doing math by hand so they
calibrated the rope by tieing knots at intervals so the natural unit
was one arc minute at the equator and called it a "knot".

My buddy who was headed to hawaii put both GPSes in the oven in the
galley and after three days was able to get one of them to work a few
minutes  a couple times a day.  That was enough.  But he said he was
within maybe 15 miles of where he thought he was

Basically your estimated course line intersected with a line of
latitude gives you longitude.

On Tue, Jan 24, 2012 at 8:50 AM, Azelio Boriani
azelio.boriani@screen.it wrote:

days

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

--

Chris Albertson
Redondo Beach, California

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

have you ever tried to measure an angular distance using a hand held
instrument while standing on the deck of a moving boat in the open
ocean?  try it and you will see why they wanted a clock.    You
really can't measure an arc minute reliably we should expect about 15
arc minute accuracy if you are standing on a moving ship.  A few very
skilled people could do better.

The moon moves what? about 10 degrees per day so in practical terms
you can get time to about 30 minutes.  But other sources of error
would add to that.  But still knowing even the hour is very good
that puts you in the correct time zone

On Tue, Jan 24, 2012 at 9:54 AM, jmfranke jmfranke@cox.net wrote:

--

Chris Albertson
Redondo Beach, California

[snip]
Then you measure

Nope. A knot is a unit of velocity, not didtance.

A "knot" is 1 nautical mile per hour
A nautical mile is that distance, subtended at the earth's surface at
the equator, by 1 arc-minute.

If somebody tells you the ship was going "22 knots/hour" they don't know
what they are talking about. A knot/hour is an acceleration.

I've only seen knots/hour used correctly once, in an inertial guidance
system, for cross-track acceleration.

-John

====================

Hi,

   Here's a little experiment I did while on last summer's Eclipse trip near Tahiti on a ship.  I brought along my Sony short wave receiver and a Sony loop antenna. I went out on the deck and did a null and recorded the bearing to WWV, WWVH and JJY. I was able to read the null to within better than 5deg. I was hoping to hear a local LFMF broadcast station in the island group, but didn't get that far. That would have given me a better LOP (line of position) It wasn't extremely accurate but fun.

    Another time I was sailing to San Clemente Is off of San Diego and about midway my friend wanted to know how far we had sailed. I took out his pelorus (hand held compass) and a small AM radio and did a null bearing from KNX and KSDO which were at about right angles to each other. I later estimated I was well within a mile of our true position. 
     Doug

From: Bob Camp lists@rtty.us
To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com
Sent: Tuesday, January 24, 2012 10:13 AM
Subject: Re: [time-nuts] establishing your position w/o gps

Hi

If you spend some time on the auction sites you can find some fairly good
(though not brand name) sextants on the cheap.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Chris Albertson
Sent: Tuesday, January 24, 2012 12:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] establishing your position w/o gps

If you want to try your hand at position determination in the pre
radio nav days you can buy a "studen sextent"  It's a low cost plastic
instrument sells for about $60.  Better ones start at $200 with $500
to $800 for a good one.   But it required much pratice and training to
outgrow the plastic instrument.    I took the class.    I think most
anyone who wants to sail on the ocean had better take the class just
in case their GPS fails.   I know some one who had both his primary
and backup GPSes fail and he was still a week from Hawaii.   They had
to revert to the old techniques from the 1700's

Much of pre-GPS position determination is not about finding your
latitude and longitude.  That is a modern notion.    What they did and
what sailors still do is find a "line of position".  That means "I am
some place on this line but I don't know where on the line"  There are
many ways to do this and they would work every method and find several
lines.   If they could see land they could shoot a compass bearing and
draw a reciprocal bearing and know they were on that line.  They would
know the ship's heading and could estimate drift and know course over
ground was parallel to that.  They could always find a latitude line.
Then if they did this right some of these lines would roughly
intersect and they would know the position without need to know
longitude.   There were other methods to find lines that required an
estimate of your speed and without clocks they resorted to chants and
songs (jo ho, jo ho,...)  As long as you sing the old pirate song at
the same tempo every time you have a decent clock.  Then you measure
distance by tossing a big chunk of lumber overboard with a measured
rope tied to it.  The captains hated doing math by hand so they
calibrated the rope by tieing knots at intervals so the natural unit
was one arc minute at the equator and called it a "knot".

My buddy who was headed to hawaii put both GPSes in the oven in the
galley and after three days was able to get one of them to work a few
minutes  a couple times a day.  That was enough.  But he said he was
within maybe 15 miles of where he thought he was

Basically your estimated course line intersected with a line of
latitude gives you longitude.

On Tue, Jan 24, 2012 at 8:50 AM, Azelio Boriani
azelio.boriani@screen.it wrote:

days

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

--

Chris Albertson
Redondo Beach, California

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

On Tue, Jan 24, 2012 at 10:31 AM, J. Forster jfor@quikus.com wrote:

You are using modern terminology.  In the days when they tossed a
real log overboard and measured time by singing a song.  Issac Newton
was still 100+ years in the future and no one new calculus or what
"acceleration" was.  Most sailors could not count to 100 out load and
many could not even write their own name.    I doubt they used the
terms as precisely as we do now.  History seems to only teach us
about the top tier, the Royal Navy and their educated officers and the
explorers like Cook and Magellan.  Most were not nearly at that level
of competence.  Most captains followed "cook book"  like directions
and did not understand the theory.

Chris Albertson
Redondo Beach, California

I managed to score a Davis Mark 25 sextant off of ebay for under 100
dollars. it's taken a fairly large amount of practice but I'm able to
get my position to a bit north of a mile.

It's a fun skill to acquire, and  has lead me off in several other fun
hobby tangents.

-Eric

On Tue, Jan 24, 2012 at 10:13 AM, Bob Camp lists@rtty.us wrote:

--
--Eric

Eric Garner

The Lunar Distance method was not practical, but it was supported by the
astronomers who felt that a mechanical contraption was beneath the art. Even
Newton, who was the first head of the Longitude Board, would not consider
the use of a mechanical clock. One argument from the astronomers was that
astronomy could determine time but a clock could only keep time.

John  WA4WDL

From: "Chris Albertson" albertson.chris@gmail.com
Sent: Tuesday, January 24, 2012 1:26 PM
To: "Discussion of precise time and frequency measurement"
time-nuts@febo.com
Subject: Re: [time-nuts] establishing your position w/o gps