For an educated person with some patience and simple tools, finding latitude is easy.

Finding longitude is not so easy. In the absence of GPS or communications, you need to measure the position in the sky of a pair of stars, AND know the current time at some reference longitude (which, for the Poms, was Greenwich). Stable marine chronometers were invented in the mid 19th century: before that, you were relying on the skies.

Since the 15th century various astronomical methods for determining the reference time. Amerigo Vespucci used the expected time of a conjunction of Mars and the Moon to estimate the time (and hence longitude) in 1499. Galileo recommended a means of using the timing of various events related to the movement of the big moons of Jupiter, and this was used quite a bit on land: it was hard to use a telescope on a ship even in very calm waters.

From the mid 18th century to the mid 19th, a method called Lunar distance was employed. It required the measurement of the altitude of a major star, the altitude of the moon, and the angle between them. This angle would then be compared to very precise celestial almanacs, listing the expected distance from the moon to various bright stars at 3 hour intervals every day over several years. Compiling those almanacs must have been quite a job, as it required solving three body gravity problems using numerical methods: tens of thousands of times for each star listed.

On land, the precision of the method was around quarter of a degree of longitude (up to 28 km). At sea, in calm waters, the precision was in effect more like a degree (around 110 km): this may seem like a lot but it was a big step up from previous methods.

dv said:

On land, the precision of the method was around quarter of a degree of longitude (up to 28 km). At sea, in calm waters, the precision was in effect more like a degree (around 110 km): this may seem like a lot but it was a big step up from previous methods.

Still easily enough to get you killed.

Look up ‘‘Admiral Sir Cloudesley Shovell’.

captain_spalding said:

dv said:

On land, the precision of the method was around quarter of a degree of longitude (up to 28 km). At sea, in calm waters, the precision was in effect more like a degree (around 110 km): this may seem like a lot but it was a big step up from previous methods.

Still easily enough to get you killed.

Look up ‘‘Admiral Sir Cloudesley Shovell’.

Amusing but note that the cloud shovel died quite some time before the lunar distance method was developed.

dv said:

For an educated person with some patience and simple tools, finding latitude is easy.

Finding longitude is not so easy. In the absence of GPS or communications, you need to measure the position in the sky of a pair of stars, AND know the current time at some reference longitude (which, for the Poms, was Greenwich). Stable marine chronometers were invented in the mid 19th century: before that, you were relying on the skies.

Since the 15th century various astronomical methods for determining the reference time. Amerigo Vespucci used the expected time of a conjunction of Mars and the Moon to estimate the time (and hence longitude) in 1499. Galileo recommended a means of using the timing of various events related to the movement of the big moons of Jupiter, and this was used quite a bit on land: it was hard to use a telescope on a ship even in very calm waters.

From the mid 18th century to the mid 19th, a method called Lunar distance was employed. It required the measurement of the altitude of a major star, the altitude of the moon, and the angle between them. This angle would then be compared to very precise celestial almanacs, listing the expected distance from the moon to various bright stars at 3 hour intervals every day over several years. Compiling those almanacs must have been quite a job, as it required solving three body gravity problems using numerical methods: tens of thousands of times for each star listed.

On land, the precision of the method was around quarter of a degree of longitude (up to 28 km). At sea, in calm waters, the precision was in effect more like a degree (around 110 km): this may seem like a lot but it was a big step up from previous methods.

I never did find out why nobody could use an accurate equation for the Moon’s motion to improve on that 110 km.

mollwollfumble said:

dv said:

For an educated person with some patience and simple tools, finding latitude is easy.

Finding longitude is not so easy. In the absence of GPS or communications, you need to measure the position in the sky of a pair of stars, AND know the current time at some reference longitude (which, for the Poms, was Greenwich). Stable marine chronometers were invented in the mid 19th century: before that, you were relying on the skies.

Since the 15th century various astronomical methods for determining the reference time. Amerigo Vespucci used the expected time of a conjunction of Mars and the Moon to estimate the time (and hence longitude) in 1499. Galileo recommended a means of using the timing of various events related to the movement of the big moons of Jupiter, and this was used quite a bit on land: it was hard to use a telescope on a ship even in very calm waters.

From the mid 18th century to the mid 19th, a method called Lunar distance was employed. It required the measurement of the altitude of a major star, the altitude of the moon, and the angle between them. This angle would then be compared to very precise celestial almanacs, listing the expected distance from the moon to various bright stars at 3 hour intervals every day over several years. Compiling those almanacs must have been quite a job, as it required solving three body gravity problems using numerical methods: tens of thousands of times for each star listed.

On land, the precision of the method was around quarter of a degree of longitude (up to 28 km). At sea, in calm waters, the precision was in effect more like a degree (around 110 km): this may seem like a lot but it was a big step up from previous methods.

I never did find out why nobody could use an accurate equation for the Moon’s motion to improve on that 110 km.

The limit was not the accuracy of the equation, but the accuracy of measuring angles using a sextant on a rocking ship.

I dissent.

The method was publicised in Petri Apiani’s ‘Cosmographia . Petri Apiani’ in 1524.

The method was well known and widely employed long before Shovell’s time. He would certainly have been aware of it, and, there being no better method as you say, used it.

dv said:

The limit was not the accuracy of the equation, but the accuracy of measuring angles using a sextant on a rocking ship.

That can be a bugger. Which is why, whenever possible, you don’t rely on a single sight. You take three if you can, maybe four or five if you’re able, and compare them.

Then you look at the Navstar/GPS to see how well your sums turned out.

captain_spalding said:

I dissent.

The method was publicised in Petri Apiani’s ‘Cosmographia . Petri Apiani’ in 1524.

The method was well known and widely employed long before Shovell’s time. He would certainly have been aware of it, and, there being no better method as you say, used it.

From what I can gather, Apianus made observations on the use of the position of the moon for telling the time, but the Lunar distance method is a specific methodology not published til the 18th century.

captain_spalding said:

dv said:

The limit was not the accuracy of the equation, but the accuracy of measuring angles using a sextant on a rocking ship.

That can be a bugger. Which is why, whenever possible, you don’t rely on a single sight. You take three if you can, maybe four or five if you’re able, and compare them.

Then you look at the Navstar/GPS to see how well your sums turned out.

So what is wrong with using crux?

roughbarked said:

captain_spalding said:

dv said:

The limit was not the accuracy of the equation, but the accuracy of measuring angles using a sextant on a rocking ship.

That can be a bugger. Which is why, whenever possible, you don’t rely on a single sight. You take three if you can, maybe four or five if you’re able, and compare them.

Then you look at the Navstar/GPS to see how well your sums turned out.

So what is wrong with using crux?

For what?

dv said:

roughbarked said:

captain_spalding said:

That can be a bugger. Which is why, whenever possible, you don’t rely on a single sight. You take three if you can, maybe four or five if you’re able, and compare them.

Then you look at the Navstar/GPS to see how well your sums turned out.

So what is wrong with using crux?

For what?

Navigation.

dv said:

captain_spalding said:

I dissent.

The method was publicised in Petri Apiani’s ‘Cosmographia . Petri Apiani’ in 1524.

The method was well known and widely employed long before Shovell’s time. He would certainly have been aware of it, and, there being no better method as you say, used it.

From what I can gather, Apianus made observations on the use of the position of the moon for telling the time, but the Lunar distance method is a specific methodology not published til the 18th century.

May have been a state-secret for whoever invented it?

roughbarked said:

dv said:

roughbarked said:

So what is wrong with using crux?

For what?

Navigation.

Be more specific. Describe your method for using Crux to calculate longitude.

dv said:

roughbarked said:

dv said:

For what?

Navigation.

Be more specific. Describe your method for using Crux to calculate longitude.

You mean you don’t know?

roughbarked said:

dv said:

roughbarked said:

Navigation.

Be more specific. Describe your method for using Crux to calculate longitude.

You mean you don’t know?

To my mind Crux would not be very suitable because it is so far from the ecliptic.

dv said:

captain_spalding said:

I dissent.

The method was publicised in Petri Apiani’s ‘Cosmographia . Petri Apiani’ in 1524.

The method was well known and widely employed long before Shovell’s time. He would certainly have been aware of it, and, there being no better method as you say, used it.

From what I can gather, Apianus made observations on the use of the position of the moon for telling the time, but the Lunar distance method is a specific methodology not published til the 18th century.

The lunar method is when you measure the separation between the Moon and a particular star. Based on that separation, you use a book of tables to look up the predicted time at a reference point such as e.g. Greenwich. The difference between that reference time and the local time aboard ship gives approximate longitude.

So, you are using the Moon to ‘tell the time’. In effect, it’s your chronometer, providing you with a sort of Greenwich Hour Angle.

Johannes Werner published it in 1514, and Apiani discussed it in detail in 1524.

Much of the computational work on the Nautical Almanac and Ephemeris was done by this lady.

https://en.wikipedia.org/wiki/Mary_Edwards_(human_computer)

Fortunately, her husband took the credit…

dv said:

roughbarked said:

dv said:

Be more specific. Describe your method for using Crux to calculate longitude.

You mean you don’t know?

To my mind Crux would not be very suitable because it is so far from the ecliptic.

in the minds eye of thine.

dv said:

roughbarked said:

dv said:

Be more specific. Describe your method for using Crux to calculate longitude.

You mean you don’t know?

To my mind Crux would not be very suitable because it is so far from the ecliptic.

You can’t see Crux north of 27 deg N.

captain_spalding said:

dv said:

roughbarked said:

You mean you don’t know?

To my mind Crux would not be very suitable because it is so far from the ecliptic.

You can’t see Crux north of 27 deg N.

I don’t live there.

captain_spalding said:

dv said:

captain_spalding said:

I dissent.

The method was publicised in Petri Apiani’s ‘Cosmographia . Petri Apiani’ in 1524.

The method was well known and widely employed long before Shovell’s time. He would certainly have been aware of it, and, there being no better method as you say, used it.

From what I can gather, Apianus made observations on the use of the position of the moon for telling the time, but the Lunar distance method is a specific methodology not published til the 18th century.

The lunar method is when you measure the separation between the Moon and a particular star. Based on that separation, you use a book of tables to look up the predicted time at a reference point such as e.g. Greenwich. The difference between that reference time and the local time aboard ship gives approximate longitude.

So, you are using the Moon to ‘tell the time’. In effect, it’s your chronometer, providing you with a sort of Greenwich Hour Angle.

Johannes Werner published it in 1514, and Apiani discussed it in detail in 1524.

Okay well let’s not be a cross purposes. I love you like a brother man.

Using the moon to tell the time was written about for quite a long time. Galileo wrote on it too.

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

dv said:

captain_spalding said:

dv said:

From what I can gather, Apianus made observations on the use of the position of the moon for telling the time, but the Lunar distance method is a specific methodology not published til the 18th century.

The lunar method is when you measure the separation between the Moon and a particular star. Based on that separation, you use a book of tables to look up the predicted time at a reference point such as e.g. Greenwich. The difference between that reference time and the local time aboard ship gives approximate longitude.

So, you are using the Moon to ‘tell the time’. In effect, it’s your chronometer, providing you with a sort of Greenwich Hour Angle.

Johannes Werner published it in 1514, and Apiani discussed it in detail in 1524.

Okay well let’s not be a cross purposes. I love you like a brother man.

Using the moon to tell the time was written about for quite a long time. Galileo wrote on it too.

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

OK.

dv said:

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

captain_spalding said:

dv said:

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

Killed how?

Witty Rejoinder said:

captain_spalding said:

dv said:

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

Killed how?

Wehn you think that those rocks are farther to the west than they are, because you’re not as far east as you think you are.

Witty Rejoinder said:

captain_spalding said:

dv said:

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

Killed how?

hit something hard in a boat. like rocks and stuff. drown.

ChrispenEvan said:

Witty Rejoinder said:

captain_spalding said:

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

Killed how?

hit something hard in a boat. like rocks and stuff. drown.

That’ll do it.

captain_spalding said:

dv said:

The method called Lunar distance was a practical, easy to use methodology that would a) work at sea and b) didn’t require the navigator to do hours of calculations, and c) gave decent accurate answers. This thread is about that particular method.

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

It really came down to John Harrison who was really only a carpenter, like that Jesus fella.

roughbarked said:

It really came down to John Harrison who was really only a carpenter, like that Jesus fella.

Carpenters…is there anything they can’t do?

Oh, yes – build a boat cabin that isn’t like a fruit box,all right-angles and straight lines.

captain_spalding said:

Witty Rejoinder said:

captain_spalding said:

My point is that it’s pretty dodgy, and people got killed using it.

As a rough and ready method, where all you have to do is measure/estimate the number of ‘lunars’ between the Moon and the star, and then compare that with a table in a book to get an approximation, then yes, it’s better than nothing.

There were some diehards, who fought against the new-fangled method with its fancy chronometers and what-have-you (they’d probably be Trump voters today, talking in feet and inches), but any mariner with a few working brain cells soon realised that the method that was less likely to get you killed was worth the effort of the calculations involved..

Killed how?

Wehn you think that those rocks are farther to the west than they are, because you’re not as far east as you think you are.

Righto.

Witty Rejoinder said:

captain_spalding said:

Witty Rejoinder said:

Killed how?

Wehn you think that those rocks are farther to the west than they are, because you’re not as far east as you think you are.

Righto.

Whisky a go go.. on the rocks we go.

Although longitude is often presented as a boon for mariners, it should also be noted that these improvements aided the creation of more precise maps of known locations on land. Previously, maps of the world were pretty good in the latitude department but wayyyy off in longitude. The quality improves out of sight from around 1550 to 1700.

roughbarked said:

Witty Rejoinder said:

captain_spalding said:

Wehn you think that those rocks are farther to the west than they are, because you’re not as far east as you think you are.

Righto.

Whisky a go go.. on the rocks we go.

Lesson 1 in navigation:

Big yellow features on the chart – avoid them.

dv said:

Although longitude is often presented as a boon for mariners, it should also be noted that these improvements aided the creation of more precise maps of known locations on land. Previously, maps of the world were pretty good in the latitude department but wayyyy off in longitude. The quality improves out of sight from around 1550 to 1700.

Yeah, surveyors and cartographers loved it. Really made it worth going to work in the morning.

dv said:

Although longitude is often presented as a boon for mariners, it should also be noted that these improvements aided the creation of more precise maps of known locations on land. Previously, maps of the world were pretty good in the latitude department but wayyyy off in longitude. The quality improves out of sight from around 1550 to 1700.

and the new news is?

captain_spalding said:

roughbarked said:

It really came down to John Harrison who was really only a carpenter, like that Jesus fella.

Carpenters…is there anything they can’t do?

Oh, yes – build a boat cabin that isn’t like a fruit box,all right-angles and straight lines.

carpenters eh? https://mb.nawcc.org/threads/late-1830s-fusee-with-massey-3-escapement-but-where-was-it-made.163316/#post-1310883

Here’s an example of the entries in the Nautical Almanac