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Old 17-10-2009, 08:37   #1
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What Time Device...

do you use and recommend for astro navigation? I've been looking on the net but can't pick something accurate and suitable for a reasonable price.
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Old 17-10-2009, 09:07   #2
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What about a handheld GPS?
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Old 17-10-2009, 09:18   #3
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$15 Casio watch--gains a stable 6 seconds per month.
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Old 17-10-2009, 09:23   #4
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When we did celestial nav on a trip we bought 3 $5 digital watches and determined their rates by WWV. We kept checking during the trip, they never varied their rates.

John
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Old 17-10-2009, 10:54   #5
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gps.....

use the clock on your GPS display... and while your at it... note the lat lon!!
Seriously... i guess just a cheap digital watch, you need to adjust it to the time tick on the SSB/hamradio... There are no clocks that are conssitantly accurate enough... unless you want to spend a lot of money..
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Old 17-10-2009, 11:35   #6
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What freq do you find the time tick on?
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Old 17-10-2009, 12:55   #7
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5, 10, 15 MHz.

cheers,
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Old 23-10-2009, 08:49   #8
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I think almost any quartz watch that is easy to read will work. I use a $30 Timex. Set the time using the GPS time and track the change over a month. That will give you your rate of change to calculate watch error.

I'm able to set mine via GPS at the start of a passage and use the time right off of the watch for the first couple of weeks. After that I'd need to make adjustments but I just resync with GPS time.
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Old 23-10-2009, 09:42   #9
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The time clock broadcasting on WWV (5, 10, 15, 20, 25 mhtz) contains UTC or UT3 time, this is time based on an Atomic Clock. There are 5 different UT times:
UT0 is solar time based on the earth's motion around the sun. However, the earth does not "circle" the sun - strictly speaking we "oval" the sun so that clock varies with where the earth is in its orbit of the sun.
UT1 - is the time used by astronomers/celestrial navigation and is an averaged UT0.
UT2 - is the smoothed time based on the rotation of the earth which is also not uniform as our planet wobbles
UTC (UT3) is the Atomic Clock time
UT4 - is a new time used for satellites in orbit around the earth which takes into account their speed which causes relativistic variation in the time. Those astronauts don't age as fast as we earth huggers do. This also includes GPS time. Corrections are sent up to the satellites to correct the time back to UTC as necessary.
- - The broadcast on HF of UTC contains the correction factor to convert UTC to Celestrial Navigation time. Between the "on the minute beep" and the first second's "tock" there are "double ticks" broadcast. These are the corrections to UTC to get UT1 (navigation time). The maximum error between the two is limited to .9 seconds. Counting the double ticks tells you to add or subtract the proper tenths of a second to derive Navigation (Celestrial) time. One second of clock time error equals about 1/4nm (about 1,500 feet) of error in your plot.
>>>>>
How does Global Positioning System (GPS) time differ from Coordinated Universal Time (UTC)?
GPS time differs from UTC by the integer number of leap seconds that have occurred since the GPS time scale begam on January 6, 1980. This difference equaled 13 seconds at the end of 2004.The integer-second difference is included in the GPS broadcast message, and is usually applied automatically so that GPS clocks display the same hours, minutes, and seconds as UTC clocks.
GPS time also differs from UTC by a small number of nanoseconds (nearly always < 25 ns) that continuously changes. The small number of nanoseconds represents the difference between the GPS time scale on-time marker (OTM) and an estimation of the OTM for the UTC time scale maintained by the United States Naval Observatory, called UTC(USNO). The current difference between the UTC(USNO) estimate and GPS time is also part of the GPS broadcast message. GPS timing receivers generally apply this correction to their 1 pulse per second (pps) timing signals, so that the received 1 pps signal represents a real-time estimation of UTC(USNO). UTC(NIST) and UTC(USNO) are kept in very close agreement, and can be considered equivalent for nearly all purposes.<<<<
- - As I tell my wife, time is a variable, and she stills looks half her age.
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Old 23-10-2009, 09:52   #10
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Apparently a standard quartz clockwork is perfectly sufficient:

"If a quartz wristwatch is "rated" by measuring it against an atomic clock's time broadcast, and the wristwatch is worn on one's body to keep its temperature constant, then the corrected time will easily be accurate within 10 seconds per year. This is more than adequate to perform celestial navigation."
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Old 23-10-2009, 17:03   #11
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A quick Google yealded the following:

Seiko Global Atomic Travel Alarm Clock w/Flashlight - Magellan's Travel Supplies


Global Atomic Clock - Magellan's Travel Supplies


Amazon.com: Global Atomic Travel Alarm Clock Digital Multi Band World Radio Controlled RC339EL Silver: Electronics

I have an older Radio Shack model that works great but is no longer sold.

Best of luck,

Paul
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Old 23-10-2009, 17:07   #12
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My digital wristwatch gains 2 mins a month!
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Old 23-10-2009, 17:47   #13
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Usea gps for time on your celestial navigation? What do you need the sextant for. I wear a Breitling chronometer - 1-2 seconds/yr - could buy a drawer full of GPSs for what the watch cost.
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Old 23-10-2009, 21:42   #14
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Those global atomic alarm clocks are a scam. It only means you can set the time zones for the world, they still need to be within range of a transmitter that sends out the time signal... which is not global. I believe there's some clocks that can receive both US and EU transmitters but neither are received by my clock in the Caribbean.

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Old 23-10-2009, 21:55   #15
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Quote:
Originally Posted by osirissail View Post
The time clock broadcasting on WWV (5, 10, 15, 20, 25 mhtz) contains UTC or UT3 time, this is time based on an Atomic Clock. There are 5 different UT times:.................... As I tell my wife, time is a variable, and she stills looks half her age.
Nice post Osiri.. thanks for taking the time () to write it and to explain these various times so clearly.
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