Determining correct "local" time at sea

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M

manus

.
Nov 5, 2011
13
Westsail 32 Vallejo
Knowing that one can obtain (1) correct UTC time via either WWV or WWVH on SSB radio or via GPS while at sea and other than (2) figuring out the longitude that delineates "local" time from Greenwich, England (=15 degree increments), what are other tried and true ways of determining "local" time in the middle of the Atlantic or Pacific oceans?

For example, sailing from CA to HI, one goes from -8 UTC to -10 UTC time zones. One needs "local" time to adjust computer time, watch schedules, etc.

Thank you.
 
Caboteur

Caboteur

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Feb 21, 2010
362
Beneteau 31 016 St-Lawrence river
Why have local time? No one else will be on "your" local time!
On all four of my crossings we kept the departure local time and adjusted all clocks & other timekeeping apparatus after landfall.
We didn't rotate watches; the change in longitude did it for us. Computers and GPS are on UTC and simply have an offset for local time.
One of the pleasures of being at sea is not really caring what time it is; around the time of the sun zenith is a good time for a beer! Spinnakers should come down before the sun does. Laying out the fishing line is done at sunrise etc...
You need precise time for astronavigation, for everything else; who cares!
Enjoy your trip, have one around local noon for me!
Pierre
 
RichH

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Just shoot a "noonsite"/LAN is the best way ...

Also dont forget to change +/- hrs. offset vs. UTC on your GPS based on your last 'fix' .... and that will yield GPS time corrected for 'local'. Some GPS will make this ∆t/UTC correction automatically, but not all. Too much hassle, just use UTC - easier.
 
Jackdaw

Jackdaw

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Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Caboteur said:
Why have local time? No one else will be on "your" local time!
On all four of my crossings we kept the departure local time and adjusted all clocks & other timekeeping apparatus after landfall.
We didn't rotate watches; the change in longitude did it for us. Computers and GPS are on UTC and simply have an offset for local time.
One of the pleasures of being at sea is not really caring what time it is; around the time of the sun zenith is a good time for a beer! Spinnakers should come down before the sun does. Laying out the fishing line is done at sunrise etc...
You need precise time for astronavigation, for everything else; who cares!
Enjoy your trip, have one around local noon for me!
Pierre
Click to expand
+1, plus it plays havoc with watch rotations.
 
Sailm8

Sailm8

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Feb 21, 2008
1,751
Hunter 29.5 Punta Gorda
Just finished a 16 day transatlantic cruise on a passage liner. East to West Barcelona to Galveston TX. Every night the chi announced that we would set back the clocks one hour. Worked great. Slept and extra hour every night and no jet lag on arrival. Of course we were moving at 20kts.
 
P

Plumper II

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Dec 14, 2009
26
Truant 33 pilothouse Victoria
Meridian passage = local apparent noon. You don't even need to be really accurate if you get the minutes from a time check. But like Caboteur says, why bother? Just ask the next guy you see what time he has.
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Local apparent noon and sun altitude and a good watch are the basics of what you need to fix your noon position.
 
Tom J

Tom J

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Sep 30, 2008
2,325
Catalina 310 Quincy, MA
We would usually go by "boat time" while on a passage in order to maintain the watch rotation. The clock at the helm remained at whatever time it was at when we left port. However, everyone has to remember to keep to that clock's time. At the end of one watch, my relief didn't show up, and I had to roust him from his bunk. He had looked at his cell phone, and thought he had another hour to go until his watch.
 
Brian D

Brian D

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Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
No one mentioned the Equation of Time table.

If you know your longitude, and you have a means of getting UTC either via GPS or SSB, then with the Equation of Time table you will know when local noon hits your meridian. I really don't think you need a sextant to do this. The Equation of Time table is for that solar day regardless of where one is located.

Just my two cents worth.
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Brian , that is exactly right but you need the sextant to determine when the sun was on the meridian.
 
Brian D

Brian D

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Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
Ross, agree. However, a good compass and a good watch that is fairly accurate should be enough. If the watch is set to UTC, and one's compass can pinpoint SOUTH accurately enough (not counting magnetic declination), then all one does is check the Equation of Time table to determine when the sun cross one's meridian. If one needed to know exactly were where they were latitude wise, then a sextant is a must (assuming one does not have a GPS).

This may not be the most scientific approach, but I think it would be accurate enough both in time and in longitude.
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
We could both make landfall after crossing an ocean with this much knowledge.
 
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