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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: New Moon, Perigee, and Solstice
From: Frank Reed CT
Date: 2004 Jan 7, 04:50 EST
From: Frank Reed CT
Date: 2004 Jan 7, 04:50 EST
George Huxtable wrote:
"The delay, between the moment of New or Full Moon (or syzygy, a favourite word of mine) and the greatest range of tide near to it (spring tide), has had the name for many years 'the age of the tide'. Not a perfect name, perhaps, but if Frank Reed and Trevor Kenchington had both used it consistently, much misunderstanding would have been avoided."
The expression "age of the tide" is so close to being obsolete (in the formal OED sense) that it's hard to see how it could help. If the expression were at all common, I agree that it would be useful, but it's not.
That said, for the remainder of this message, I will use "age of the tide" in its old sense.
George H also wrote:
"My own experience supports the statement in the Admiralty Manual of Tides "The average value of the age is about 1 to 1 1/2 days" "
Something to think about: what does "average" mean here (I'm serious)? Do you believe that this "average" applies globally with no regional variations (and I don't mean just local random variations but actual regional patterns)?
And George H wrote:
"perhaps in some parts of Europe 2 days."
Maybe even, dare I say it, THREE days?? ;-) The "age of the tide" is unusually large in northwest Europe. There are other places globally with ages of three days, including the Sea of Okhotsk and an intricate pattern in Indonesia (which has an intricate pattern for practically any tidal parameter you might name).
And George H wrote:
" I think that Cassini, who I quoted in an earlier mailing, got the age of the tide about right, at 1 day to the West of the English Channel, 2 days to the East"
At Brest, it's close to one day. But the lag rises rapidly. Do you have access to a set of harmonics for northwest Europe? The UKHO made them rather difficult to acquire a few years ago.
And George Huxtable wrote:
" Well, I simply ask Frank to supply some evidence to support his own claims about that three-day "age", on which he has built such a big argument."
Big argument?? Maybe I missed something in my own words! On this list, that wouldn't surprise me... How would you characterize my "big argument" about the age of the tide? I asked a simple question about Bowditch which Dan Allen kindly answered. Other issues about tides certainly interest me (I do know a "little something" about the matter), but I'm not aware of any "big argument".
So George, do you know how to calculate the "age of the tide" from the harmonic constituents for a given port? Do you know how these numbers look for various places in Europe and for points in the Americas (which was the original relevance of my Bowditch question)? Should I describe how it's done? I've considered assembling a map, but it would be a bit time-consuming.
Frank E. Reed
[X] Mystic, Connecticut
[ ] Chicago, Illinois
"The delay, between the moment of New or Full Moon (or syzygy, a favourite word of mine) and the greatest range of tide near to it (spring tide), has had the name for many years 'the age of the tide'. Not a perfect name, perhaps, but if Frank Reed and Trevor Kenchington had both used it consistently, much misunderstanding would have been avoided."
The expression "age of the tide" is so close to being obsolete (in the formal OED sense) that it's hard to see how it could help. If the expression were at all common, I agree that it would be useful, but it's not.
That said, for the remainder of this message, I will use "age of the tide" in its old sense.
George H also wrote:
"My own experience supports the statement in the Admiralty Manual of Tides "The average value of the age is about 1 to 1 1/2 days" "
Something to think about: what does "average" mean here (I'm serious)? Do you believe that this "average" applies globally with no regional variations (and I don't mean just local random variations but actual regional patterns)?
And George H wrote:
"perhaps in some parts of Europe 2 days."
Maybe even, dare I say it, THREE days?? ;-) The "age of the tide" is unusually large in northwest Europe. There are other places globally with ages of three days, including the Sea of Okhotsk and an intricate pattern in Indonesia (which has an intricate pattern for practically any tidal parameter you might name).
And George H wrote:
" I think that Cassini, who I quoted in an earlier mailing, got the age of the tide about right, at 1 day to the West of the English Channel, 2 days to the East"
At Brest, it's close to one day. But the lag rises rapidly. Do you have access to a set of harmonics for northwest Europe? The UKHO made them rather difficult to acquire a few years ago.
And George Huxtable wrote:
" Well, I simply ask Frank to supply some evidence to support his own claims about that three-day "age", on which he has built such a big argument."
Big argument?? Maybe I missed something in my own words! On this list, that wouldn't surprise me... How would you characterize my "big argument" about the age of the tide? I asked a simple question about Bowditch which Dan Allen kindly answered. Other issues about tides certainly interest me (I do know a "little something" about the matter), but I'm not aware of any "big argument".
So George, do you know how to calculate the "age of the tide" from the harmonic constituents for a given port? Do you know how these numbers look for various places in Europe and for points in the Americas (which was the original relevance of my Bowditch question)? Should I describe how it's done? I've considered assembling a map, but it would be a bit time-consuming.
Frank E. Reed
[X] Mystic, Connecticut
[ ] Chicago, Illinois
