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Old 13-04-2014, 04:00   #16
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Re: The Importance Of The Noon Sight?

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Originally Posted by goboatingnow View Post
Personally I prefer star sights., proper fix

Dave
Ed Zakery... but even back in the day you didn't find many yachtsmen taking stars.... lets not complicate things.

Stars by moonlight in the Red Sea... bonzer fun.... lunar eclipse in 48 hours.... don't miss it....
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Old 13-04-2014, 04:26   #17
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Re: The Importance Of The Noon Sight?

With a good star scope, and a clear sky, a good fix can be had from crossing the sun with Venus during the day (only at certain times of the year when Venus is not too close to the sun).
You need to pre calculate the alt and azimuth of Venus in order to sight it though.
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Old 13-04-2014, 04:28   #18
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Re: The Importance Of The Noon Sight?

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Originally Posted by El Pinguino View Post
Ed Zakery... but even back in the day you didn't find many yachtsmen taking stars.... lets not complicate things.



Stars by moonlight in the Red Sea... bonzer fun.... lunar eclipse in 48 hours.... don't miss it....

Back in what day, like before the 1600,s lol
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Old 13-04-2014, 04:32   #19
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Re: The Importance Of The Noon Sight?

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Originally Posted by nigel1 View Post
With a good star scope, and a clear sky, a good fix can be had from crossing the sun with Venus during the day (only at certain times of the year when Venus is not too close to the sun).
You need to pre calculate the alt and azimuth of Venus in order to sight it though.
Best done with Venus on the meridian.... is simple then
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Old 13-04-2014, 04:36   #20
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Re: The Importance Of The Noon Sight?

and also ... mer-pas Venus is listed on the daily pages... just under Zuben'ubi
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Old 13-04-2014, 05:46   #21
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Re: The Importance Of The Noon Sight?

The method of leaving the sextant set and waiting for the sun to come back down to the virtual horizon is a good shortcut in settled weather, but plotting a curve and drawing a freehand "line of best fit" is a much better method in rougher weather, when you can't guarantee to be able to see a decent approximation to a horizon very often.

- - - - -

Establishing noon on a daily basis was important before the advent of chronometers, because it was effectively rebooting all the ship's routines. Changes of watch and evolutions noted in the log, were timed from the moment the master said "Call that noon, Mr Midshipman (Wilberforce, or whatever)", and a pimply youth tipped the hourglass over.

If there was no horizon, or no sun, they would simply carry forward the time from the previous day on the assumption of a twenty four hour day and minimal error in the hourglass rate, and correct the ship's time at the earliest opportunity (maybe by another means, like taking lunar distances, if the master was fussy, or they were in a tricky situation)

They did not have time zones, and did not make adjustments of whole hours: they were constantly changing their ship's time every day.

In individual cases some of this would obviously not apply but my understanding is that the above represented fairly general practice.
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Old 13-04-2014, 17:32   #22
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Re: The Importance Of The Noon Sight?

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Originally Posted by Andrew Troup View Post
Establishing noon on a daily basis was important before the advent of chronometers, because it was effectively rebooting all the ship's routines. Changes of watch and evolutions noted in the log, were timed from the moment the master said "Call that noon, Mr Midshipman (Wilberforce, or whatever)", and a pimply youth tipped the hourglass over.

If there was no horizon, or no sun, they would simply carry forward the time from the previous day on the assumption of a twenty four hour day and minimal error in the hourglass rate, and correct the ship's time at the earliest opportunity (maybe by another means, like taking lunar distances, if the master was fussy, or they were in a tricky situation)

They did not have time zones, and did not make adjustments of whole hours: they were constantly changing their ship's time every day.

In individual cases some of this would obviously not apply but my understanding is that the above represented fairly general practice.
Many ships were doing that ( sans hourglass and spotty youth ) into the 1930's and I have even heard of a few doing it into the '50s long after time signals and stuff came along.

In the early 1960's Liberia was still keeping local time based on the longitude of Monrovia.... about 41 minutes or so behind GMT.
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Old 13-04-2014, 17:44   #23
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Re: The Importance Of The Noon Sight?

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Many ships were doing that ( sans hourglass and spotty youth ) into the 1930's and I have even heard of a few doing it into the '50s long after time signals and stuff came along.

...
Gee, who'd a thunkit!

So I guess you're saying ship's time was an analogue concept, changing in a non-granular way driven by daily position changes and ship's solar noon, until quite recently, on some ships!

... With no formal connection to GMT, which presumably the chronometers kept in custody for navigational purposes only?

Thanks for that, EP. Great what you can learn here.
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Old 13-04-2014, 18:17   #24
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Re: The Importance Of The Noon Sight?

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Gee, who'd a thunkit!

So I guess you're saying ship's time was an analogue concept, changing in a non-granular way driven by daily position changes and ship's solar noon, until quite recently, on some ships!

... With no formal connection to GMT, which presumably the chronometers kept in custody for navigational purposes only?

Thanks for that, EP. Great what you can learn here.
If 60 years ago is 'recent' for you thats fine by me.

Many ship masters in the 1930's would have gone to sea about 1880... old habits die hard etc....

I must dig out my Lecky's Wrinkles and see what he has to say on the subject... did you know there is an 'Abra Lecky's Retreat' in Patagonia? Another useful factoid for you to stow away somewhere... you never know when you will be able to insert that into a conversation.
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Old 13-04-2014, 18:42   #25
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Re: The Importance Of The Noon Sight?

El Pinguino

I suppose I was thinking it was comparatively recent, considering how long ships have had chronometers, and how long the world has had recognised time zones.
Incidentally I believe European cities did not have any sort of coordinated time until the advent of railways and the associated timetables made it imperative; they just kept local time (presumably usually based on, and corrected over time, with reference to LAN)
Do you know the backstory behind Lecky's Retreat (a location which I had not heard of)
The other burning question: Is Abra short for Abraham?
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Old 13-04-2014, 19:34   #26
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Re: The Importance Of The Noon Sight?

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Originally Posted by Andrew Troup View Post
The method of leaving the sextant set and waiting for the sun to come back down to the virtual horizon is a good shortcut in settled weather, but plotting a curve and drawing a freehand "line of best fit" is a much better method in rougher weather, when you can't guarantee to be able to see a decent approximation to a horizon very often.

- - - - -

Establishing noon on a daily basis was important before the advent of chronometers, because it was effectively rebooting all the ship's routines. Changes of watch and evolutions noted in the log, were timed from the moment the master said "Call that noon, Mr Midshipman (Wilberforce, or whatever)", and a pimply youth tipped the hourglass over.

If there was no horizon, or no sun, they would simply carry forward the time from the previous day on the assumption of a twenty four hour day and minimal error in the hourglass rate, and correct the ship's time at the earliest opportunity (maybe by another means, like taking lunar distances, if the master was fussy, or they were in a tricky situation)

They did not have time zones, and did not make adjustments of whole hours: they were constantly changing their ship's time every day.

In individual cases some of this would obviously not apply but my understanding is that the above represented fairly general practice.

Yes, Jack Aubrey is often found saying "Make it noon". I think I need to read that series a third time...
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Old 14-04-2014, 00:12   #27
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Re: The Importance Of The Noon Sight?

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Do you know the backstory behind Lecky's Retreat (a location which I had not heard of)
The other burning question: Is Abra short for Abraham?
'Abra' is local for 'opening' ( possibly from the same roots as 'abierto'). One such is is Abra Canal which lies to the east of Isla Desolacion and connects Estrecho de Magallanes to the South Pacific at that point. Abra Lecky's Retreat lies between Isla Piazza and Isla Tariba. It connects Canal Sarmiento with Canal Smyth to the west.... who knows why he was retreating. Lecky was master of the ship 'Europe' engaged in survey work thereabouts in 1872.

Moving right along... this is what he had to say about clocks ....
'At sea , it is a good plan to carry a (deck) watch set to Greenwhich Mean Time. .. This watch, then, becomes available for azimuths, ex-meridians, or other work where the exact second is not of consequence, and saves a trip to the chronometer. To have it set to Apparent Time at Ship might at first be considered preferable, but a moment's reflection will shew that this is constantly altering, and in a fast steamer on east west courses in high latitudes does so very rapidly sometimes as much as 50 minutes a day, so the watch would never be correct for an hour at a stretch. Moreover the GMT can with ease be converted into apparent time at ship, sidereal time, or any other, just as occasion may require.
After breakfast all the clocks on board should be set to Apparent Time at Ship for noon of that day as determined by dead reckoning. There is then no fear of missing 'sun time' and the plan for many reasons is preferable to the usual one of making eight bells by the sun.'

So said Lecky in his 'Wrinkles' in 1881.
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Old 14-04-2014, 00:19   #28
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Re: The Importance Of The Noon Sight?

muchas gracias, estimado seņor el Pinguino

gr8 info, makes sense 2

bright cookies, the 2 o' yez.
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Old 14-04-2014, 02:39   #29
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Re: The Importance Of The Noon Sight?

When we were using celestial, Jim used to use a Least Squares way of manipulating the noon sites observations to arrive at our position. We also used a lot of star sights. This was in about 1983, not all that long ago, really.

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Old 14-04-2014, 02:52   #30
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Re: The Importance Of The Noon Sight?

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When we were using celestial, Jim used to use a Least Squares way of manipulating the noon sites observations to arrive at our position. We also used a lot of star sights. This was in about 1983, not all that long ago, really.

Ann
To elaborate on this theme a bit:

I used a HP-41 with a "nav-pac" for sight reduction (sorry if that offends anyone... I wasn't trying to be cool, I was navigating on a small boat and trying to not be sea-sick, which I find to be stimulated by staring at nav tables).

At any rate, I had a little routine that ran on the 41 that did a least squares fit to a parabola (not a "bell curve"... really...). One took a few sights leading up to local noon, and a few afterward. Entered the data and after a few seconds of cogitation the calculator spat out a bloody good estimation of the peak of the parabola and hence the time of noon. Worked pretty well, too!

But, as Ann said, we relied primarily on star sights for fixes... when available. On that return from Hawaii, we had eleven straight days of overcast. The old DR log saved our asses ! I'm glad to have had the experience of relying on Celsetial, but I'm even glader to have a GPS or two!

Cheers,

Jim
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