What Time is it?

[pabrides]

Hello Shipmates,

As a kid and up until the age of electronic watches it was not uncommon for me and other common folk to ask a perfect stranger what time they had - even though one had a watch on the wrist or in the pocket.  We verified the accuracy of our watches as a community to help ensure we were on time.

Folks knew their watches so well they might include a disclaimer such as "I have 9:37, but Im probably fast 3 or 4 minutes."

In our town at precisely 6pm an air-raid siren would blast across the community.  One could set a watch to it.

I used to set my wind-up Timex 5 or 10 minutes ahead just to make sure I was on-time for school or work. 

One could call a phone number to get the correct local time (unsupported in the nation in which I currently reside.)

The second hand wasnt used as much to time boiling eggs as to make sure the watch still worked.

Nothing remotely like these things have happened to me in the past 30 years.

These days you are as likely to get a knife in the chest as receive some semblance of accurate time from a stranger.

Even the wearing of wrist watches has become less fashionable as cell phones increase in number, all of which give reasonable time however imperfect.

With cell phone, computer, and gps clocks being off from actual GMT, sometimes by a considerable amount, where can one go, besides WWV, to get accurate GMT?

Ive accessed several of the GMT web sites, including NIST, which say their time is accurate, but even they can differ from each other by several seconds. Knowing my chrono gains a second in about 3 days I usually set it behind a second which gives me a week of reasonably accurate GMT.

What has been your GMT reference, and how accurate has it been?

Smooth sailing
Joe

[Rdutton]

That's a good question, Joe. We have one of those "atomic clocks" on the wall and I compare my watch to it. Sometimes I'll call NIST (WWV) and get the time- 303-499-7111

The USNO has it's "master clock" which I suppose is really the most accurate time we can get.
See here- https://tycho.usno.navy.mil/what.html

Another site- Time.is (yes, it's a dot-is site) provides a similar time.

Most computers you and I have set their time to servers so you just have to assume they're very accurate too.

I've found the display of digital watches are quite satisfactory for making observations for the only reason- I don't need to interpret or think about the time I see on the display. Analog watches provide the same result and seeing the position of the hands is probably just as easy to remember. Analog watches are much more beautiful than those ugly digital ones. I'm thinking of watches that look similar to Rolex. More people have sailed around the world with analog watches/chronometers than digital ones...in the days gone by.

All of this reminds me of the W.C. Fields movie "It's a Gift"....where he and his family are eating lunch in what they think is a park (some man's yard) and W.C. compares his watch to the sundial and says to the effect that the sundial is wrong by a few minutes. His nagging wife exclaims, "oh the sundial is wrong but your watch is right!".

What do you think?

[BigBill]

time.nist.gov is where I go to update my computer time. I usually do it right before I set or check my watch to take a few sights. I have no idea how close it is to actual GMT. Can't be more than a few seconds off however. I assume there will be some error just in the transmission of a 'signal' over the internet, through servers etc.

[pabrides]

Good replies, shipmates.

I wanted to add another technique I frequently use when taking observations.  It eliminates the need to memorize the time while reaching for a pencil to record it. I dont need to worry about a flashlight at night either... I just start a stopwatch at the plot table, walk out into the night, take the shot, then return to the table and record it.

I many times us a stopwatch to record the time..  I start it on the minute exactly (or you could use any time) then immediately stop it when I have my shot.  The stopwatch time is then added to the time I started it and bingo... fairly accurate and consistent observations.  I dont have to rush because the observation time is frozen on the stop watch.

We all have concerns about using the correct method to reduce an observation, but I have not seen much concern over GMT; and everything we do CN wise hinges on accurate time.  We sort of take it for granted.

I wonder if one could consistently mark time by local observation just in case WWV or the internet services went down... How would one get the time?  I understand that Harrison used his own star observations to track sidereal time then convert it to local time...  How would that work now?? and how would you do it?? could you create your own Greenwich with your house being the mean time??? I think so

keep dry
joe

[Rdutton]

Fellas,

I forgot to mention the time signals at 2.5 mHz, 5 mHz, 10 mHz, 15 mHz and 20 mHz (WWV)

There's also WWVH (Hawaii). I you look in The Nautical Almanacs found on this site you'll see on page 6 (Useful Information) the frequency list for both stations. You'll need a SW (Short Wave) receiver to get the signals.

There's talk of shutting down both stations for govt. budget reasons.

That being said....what do you do if you don't have a watch that's accurate or is in error? Well, you could make a great effort to learn Lunars or....try the following formula.

Caution! I've been working on these formulas and they have proven to be very accurate in establishing the time within 3 or 4 seconds. You must know your exact latitude and longitude or it just wont give you the correct time of the observation. I have no idea what results they will yield in any other hemisphere except Northern and Western (northern). The formulas as presented below are as they would be entered into the Casio fx-300es calculator. Good luck!

Recovery of Time using GHA

If Zn is < 180°
NOTE! If GHA of Integral hour is before MP at Greenwich then do not use the second – 360° (minus 360 degrees)

GHA Integral Hour + ((360º – Cos-1((Sin(Hc or Ho) – Sin(latitude) x Sin(declination)) ÷ Cos(AP latitude) x Cos(declination)) + longitude – 360º – GHA of Integral Hour) ÷ 15

If GHA of Integral hour is before MP at Greenwich then do not use this formula;

GHA Integral Hour + ((360º – Cos-1((Sin(Hc or Ho) – Sin(latitude) x Sin(declination)) ÷ Cos(AP latitude) x Cos(declination)) + longitude – GHA of Integral Hour) ÷ 15

If Zn is > 180°
GHA Integral Hour + (Cos-1((Sin(Hc or Ho) – Sin(latitude) x Sin(declination)) ÷ Cos(AP latitude) x Cos(declination)) + longitude – GHA of Integral Hour) ÷ 15

[BigBill]

Time signals are hard to hear though I suppose if I listened better and more often I might get the hang of it.

[pabrides]

Time signals are hard to hear though I suppose if I listened better and more often I might get the hang of it.

I have a hard time too...Im not sure which tic or tone is XX:00 ;  The high tone, the low tone, the first no tone.....???

At one time I thought I knew, however, I dont...  can someone explain this to me?

Also, I think it would be fun if someone could create their own GMT; maybe call it by the city in which you live (say Burgertown Mean Time 'BMT')...  Then you can convert BMT to GMT by so many hours and minutes and still use the current pubs...  Any takers??

If WWV  or internet is lost how is one going to determine GMT...  There should be a host of amateurs out there willing to keep time within a few seconds using their own celestial observations...  Perhaps the local Astronomy clubs could start a time-keeping program...  Give em something new to do.   Remember - you heard it here first. I think the government scared people off the subject with all that ATOMIC CLOCK BS... That may matter for GPS, but for CN Atomic accuracy is not critical.

Go ask the average Joe on the street if he knows where in the world he is standing and I bet he wont give you lat and long to 5 decimal digits... Chances are he will name you the City, state, or country.... Hows that for accuracy?

Full steam ahead...
joe

[craigsl]

To get better reception of WWV or WWVH you have use the right frequency for the day. Daytime...typically use a higher frequency such as 10, 15 or 20 mHz. Night time....2.5, 5 or even 10 mHz. This all depends upon the Sun Spot Cycle too.

Also, use the right length antenna. A 2 foot wire isn't going to work too well. I have a Grundig Yacht Boy (shortwave radio....pretty small) and I can get WWV most of the time using the telescoping antenna provided with the radio. I also have a Kenwood TS-130s (transceiver) and can get mostly any of the broadcasts of WWV. (I hold an Extra class amateur radio license). Don't ask for my call sign as a search of it on the internet will tell you my physical address.

We, hams, use WWV to adjust the frequency reading display of our radios. So if your frequency meter is off on the radio it can be recalibrated using WWV tones through what's called "zero-beating".

Forget about the ticks of WWV....no one counts them. Here's what wikipedia says- "The format for the voice announcement is, "At the tone, X hour(s), Y minute(s), Coordinated Universal Time." The announcement is in a male voice and begins 7.5 seconds before the minute tone".

Atomic clocks, like the ones we have on the wall, are great. The only problem I heard, but don't know for a fact, is that about 800 miles away from land they are useless.

Joe, you've got the right idea for local "GMT". We do have it, sort of, it's called Zone time....and there are 24 of them. Of course, your zone time is better than mine!

I think...but am not certain....it was either Shackleton's failed Antarctic expedition or Amundsen's successful South Pole expedition who had a radio receiver aboard in which they could get time signals. It probably was Shackleton's. Obviously if it was Shackleton's, the radio "went down with the ship" and they didn't carry it with them during their escape from the ice. I do know that Frank Worsley, after they had landed on Elephant island, paced up and down the rocky beach checking his chronometer. I suspect, since they knew the latitude and longitude of their position fairly well, he could take a Sun sight and correct the chronometer accordingly.

I've tried to get other time signals from supposed other countries "time" stations but haven't gotten a single one. CHU (Canada) has driven me insane for over 40 years. Since China is really the "rising star" so to speak of countries I would expect that they have a time broadcast. However, after locating the frequency(s) they're supposedly transmitting on I've never heard them once.

If some amateur radio operator took over the transmission of time signals it frankly wouldn't be difficult. In CN we work with what's called UT1 which can be off by plus or minus 1 second. Big deal.

Best wishes shipmates,

Craig

[pabrides]

Atomic clocks, like the ones we have on the wall,  are great.  The only problem I heard, but don't know for a fact, is that about 800 miles away from land they are useless.

Joe, you've got the right idea for local "GMT".  We do have it, sort of, it's called Zone time....and there are 24 of them.  Of course, your zone time is better than mine!
 
 ... Since China is really the "rising star" so to speak of countries I would expect that they have a time broadcast.  However, after locating the frequency(s) they're supposedly transmitting on I've never heard them once.

If some amateur radio operator took over the transmission of time signals it frankly wouldn't be difficult.  In CN we work with what's called UT1 which can be off by plus or minus 1 second.  Big deal.

Shipmates,

I suppose that certain ideas Ive suggested in this thread several times now are so foreign to most people that the concept just bounces off the grey matter without penetration... or so some of the responses would suggest; either that or I'm just a horrible writer incapable of expressing same.

I am not suggesting that Hams (of which group I also belong as an extra class) rebroadcast GMT, or UT, or UTC, or whatever the governments agree to call zero time zone (although such a contingency is laudable even if the time hack broadcasts were limited to a few times a day).

Several institutions in the US including (I think) the Naval Observatory and numerous institutions of higher learning own and operate transit telescopes, exactly aligned with their meridian, with which they observe the passage of pertinent stars to facilitate the keeping of time.  I have merely suggested that local CN or astronomy enthusiasts obtain some sort of transit instrument no matter how primitive and start keeping time as though that person's home (or that group's position) in their city is the zero meridian.  The exact location would be well known and the time hack from THAT location could easily be adjusted to GMT in order to facilitate the use of contemporary almanacs.  I hope that was clear.

What I am suggesting is that we incorporate our own amateur observatories and keep our own time - such as is done by the Naval Observatory and others who coordinate with Greenwich - so that in case of Nat'l emergency we wont need to count on some government agency or sponsored facility to keep time...  We would have our own time keepers of whom we could rely to facilitate the process of celestial navigation....  I hope that was more clear.

Here is an example:

BigBill has a transit instrument at his house with which he observes the passing of certain stars over his meridian.  He keeps a well maintained clock in his house updated with that sidereal star data... he or his friend then periodically broadcast time hacks over selected HF bands for the rest of us who then adjust our own clocks and verify the accuracy of other transit instruments across the states and hopefully the globe.   Understanding and applying proper time altering phenomena to coordinate with GMT (mean time) would be easy...  And I believe the learning curve would be a short one as more time keepers (as in people who volunteer to make star observations) get involved and the practice is refined.   I hope this was very very clear.

This is a grass roots effort to ensure we have a method of keeping time in the event Government GMT time signals disappear either permanently or temporarily.  Besides, Astronomy clubs might relish the idea so as to improve their own education and sense of local importance.  There are a hundred reasons why local groups should desire to participate... There might be Boy Scout badges awarded for time keeping.   I hope this was very very very clear.

I recently contacted an Astronomy society asking for advice and procedures concerning amateur timekeeping..  Im confident they will provide good instruction or relay my questions to someone who can.

Moving on:

I have an Atomic wrist watch that I use for a chrono... it does not automatically update probably due to my distance from WWV which is about 8000 miles.

Next time I take my Yaesu FT 897D out of the box Ill hunt for those Chinese time transmitters.

Fair Winds, Shipmates; keep the ideas a-comin!!!
Joe

[CarlosPindle]

Matey,

Joe your idea is terrific and simple. I've seen photos of transit telescopes (not Transit in the sense of surveying) that are at Greenwich and have found the idea fascinating.

Oh...another thing- US power companies use 60 Hz for in power transmission and that frequency is used by electric (plugged into the wall) clocks which are as accurate as that frequency- very accurate.

No doubt the PICKY PICKY devices of life aren't satisfied with anything but 1 billionth of a second accuracy.

I'm no expert in these matters but I've often wondered why accuracy in timing of computer devices is so critical?

The USNO does provide THE MASTER CLOCK and if THEY (the USNO) doesn't keep time then we're in big trouble...and probably will end up like the first few minutes of 2001 A Space Odyssey. But it really shouldn't be difficult to send out time signals however the means.

Carlos

[BigBill]

...BigBill has a transit instrument at his house with which he observes the passing of certain stars over his meridian.  He keeps a well maintained clock in his house updated with that sidereal star data... he or his friend then periodically broadcast time hacks over selected HF bands for the rest of us who then... 

I'll set up a go fund me page immediately to purchase the necessary equipment. Do you think $100,000 will be enough? :)

[pabrides]

...BigBill has a transit instrument at his house with which he observes the passing of certain stars over his meridian.  He keeps a well maintained clock in his house updated with that sidereal star data... he or his friend then periodically broadcast time hacks over selected HF bands for the rest of us who then... 

I'll set up a go fund me page immediately to purchase the necessary equipment. Do you think $100,000 will be enough? :)

Thank you Carlos and Bill, and the rest of you for at least entertaining the idea... need more comments though....

BigBill, just use your neighbor's chimney like Harrison did... but go-fund-me sounds good too :) 

Carlos, atomic accuracy counts for guided bombs and missile systems...does that help to answer your query?   

Lets all do some research and if some of you have contacts in astronomy clubs and such perhaps this is a good time to gather them in...  Ham clubs are always looking for something new...  Happy sailing

joe

[pabrides]

Hello Shipmates,

As per a previously received suggestion,  I hunted the short-wave bands here in the Philippines to locate other time signals... of which there were none found.  However, something peculiar is happening here in this part of the world.  On the same frequencies as WWV  I found a secondary signal that compliments WWV time hacks without the other tones and voice information.  This additional signal, of which I can hardly guess the origin, ticks along with the hard to hear WWV stations and then mimics the on-the-minute time hack.  Sometimes there is a Morse code identifier - BPM - repeated several times.   In south asia this other hack is much easier to hear and seems to be accurate - or at least ticks in unison with WWV.  Any ideas?  I Google searched BPM and WWV but all I can find is a Beats Per Minute reference. 

May your sails be filled
joe

[BigBill]

Might this be it?

https://en.wikipedia.org/wiki/BPM_(time_service)

BPM is the call sign of the official short-wave time signal service of the People's Republic of China, operated by the Chinese Academy of Sciences, broadcasting from CAS's National Time Service Center in Pucheng County, Shaanxi at 34°56′55.96″N 109°32′34.93″E

Coordinates: 34°56′55.96″N 109°32′34.93″E

, roughly 70 km northeast of Lintong,[1] along with NTSC's long-wave time signal BPL on 100 kHz.
BPM is broadcast at 2.5, 5.0, 10.0, and 15.0 MHz, the same frequencies as WWV and WWVH, following the schedule listed below:[2]

BPM is idiosyncratic in that it transmits UT1 time between minutes 25 through to 29 and 55 through to 59, which creates an odd click-beep effect when heard below a stronger time signal station such as WWV especially when UT1 seconds are halfway between UTC seconds, close to a leap-second event

[pabrides]

Well, Shipmates,  it took a bit of time but a brilliant and forward thinking PHD student at Cornell University answered my question about keeping local time... enthusiastically I might add.

Below is the entire email exchange; I have taken out the addresses and names for privacy.  My initial email is at the bottom.

Read it carefully and give it a go.  Approach the astronomy and Ham radio clubs etc in your area  to get the ideas flowing.


Although it's a wonderful thing that governments have, for the last few centuries, provided accurate time for the masses, it may be time to relearn the art and technique of time keeping for ourselves and practice disseminating same.



Email exchange:


Excellent question.
I apologize for taking so long to get back to you.
>we desire to decentralize time keeping<
I have the utmost respect for this goal. In the event of a catastrophe, people like you who are prepared will be important for preserving knowledge and information and disseminating it back out to the world at large.
I was surprised that I couldn't find any guides to this by searching on the internet. When you get a working set up, please post it somewhere.
All that you'll need for this project is the location of your observatory, the RA and DEC of a few reference stars (at least one, but more is better), and a way to measure the altitude of one of the reference stars.
Quick caveat, I'll tell you how to get UTC instead of GMT, since UTC is essentially GMT without DST, and I hope that DST does not survive whatever catastrophe we are preparing for in this thought experiment.

1) Measure the altitude of the reference star, the distance from the horizon in degrees.
2) Calculate the Local Sidereal Time (the RA angle currently passing through the local meridian): LST = (90degrees - ALTreferencestar)/(cos(DECreferencestar)cos(latitudeofobservatory))
3) Convert to Greenwich Mean Sidereal Time (GMST, the RA angle currently passing through the prime meridian) using the longitude of the observatory converted into hour angles (15 degrees in an hour, the longitude is the offset of LST from GMST).
4) Convert from GMST to UTC (this is the trickiest part of the calculation, and why it took me so long to get back to you because I had to dig up an old homework from a class I took a while back and re-solve it and double check that my math matched the plots my code produced and I turned in, and I'm pretty sure this is all correct)
To do this properly, we need to calculate the ecliptic longitude (position angle) of the Earth along its orbit, including the eccentricity and argument of periapse of the Earth's orbit, which can influence the result by up to a half-hour.
Going from UTC to GMST is rather straightforward, but the reverse is a transcendental equation that we will have to approximate.
Because I have it on hand (the homework assignment was calculating/plotting an analemma), we'll do this for the Sun instead, which is 180 degrees from the position of the Earth.

From Kepler's 2nd law, to first order in eccentricity, we have:
lambda = lambda_perihelion + n(t-t_perihelion) + 2esin(n(t-t_perihelion))
Where:
n is the average angular rate of the Earth's orbit (~ 0.985647 degrees per day),
e is the Earth's eccentricity (~0.017),
lambda_perihelion is the ecliptic longitude of the Sun at the time of the last perihelion, along the ecliptic (283.59 degrees in 2015),
t_perihelion is the date of the last perihelion (~07:00 UTC on January 4th in 2015)
t is the current date
and lambda is the ecliptic longitude of the sun at the current date
You can also calculate the slight changes of t_perihelion and lambda_perihelion from the precession of the earth's orbit, but that's not going to have a significant impact on your answer for the next few hundred years, so we'll ignore that for now.

Now, to get from lambda to RA and DEC of the sun, we use the following three equations to rotate the sphere of our coordinate system:
sin(DEC) = sin(Epsilon)sin(lambda)
sin(RA)  = cos(Epsilon)sin(lambda)/cos(DEC)
cos(RA) = cos(lambda)/cos(DEC)
where Epsilon is the obliquity of the Earth (23.5 degrees)
We need two equations to determine RA because inverse trig functions are multi-valued on a domain that spans multiple quadrants, such as for RA.

Now subtract 180 degrees from the RA of the Sun to get that of the Earth (think: the direction away from the Sun is what's overhead at midnight, which is 0:00 UTC)
Now divide by 15 to go from degrees to hours (15 degrees in an hour)
This is the time, in hours between GMST and UTC, so add it to your GMST value from the previous step to get the time in UTC!

Please let me know if you have any questions, confusion, or think I made a mistake and want me to run back through the math.
And please keep me updated on your progress for implementing this! I'm honestly very interested.
I love doomsday prepping and figuring out how to decentralize our information heap instead of relying on centralized sources.

Let me know how things go,

A***** S*  F****
PhD Student
Cornell University
Department of Astronomy and Space Sciences

On Sat, Oct 20, 2018 at 4:17 PM C****** R****> wrote:
Name
 
j****
Email
 

Your Background
 
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John Harrison used the stars and his neighbors chimney to keep track of sidereal time - or so the story goes... What simple and effective astronomy procedure might one use these days to track time locally within a few seconds of GMT in the event access to WWV or other standard clock references are interrupted? I assume it would have something to do with knowing the exact location of the observatory and which best stars and their sidereal hour angles to use throughout the year. The plan for our celestial navigation group is to provide accurate time to the local community in the event of catastrophe; which would no doubt come in handy for marine navigation and other common purposes.. It seems to us that the keeping of time is taken for granted... we desire to decentralize time keeping.

Latest reply to the time-keeping instructions:

A****,

Thank you, and Mr R*****, for providing a wonderfully concise reply to my question about local time keeping.  I feel honored.

I have posted your information on the Celestial Navigation forum site where I hope the idea of time keeping will germinate and take root.  Here is the address of the thread in question:

https://thenauticalalmanac.com/Forum/sho...666#pid666

Being a Ham Radio enthusiast as well, I plan to approach our local club about disseminating time hacks.  And I plan to contact local astronomy clubs to challenge them with your time keeping process.  I think the boy-scouts might be interested in providing badges for timekeeping; at least I will address the issue with them.  

You and your peers are welcome to contribute to the forum, as your expertise is not common among us.  

I will study hard your time keeping instructions and endeavor to create an easy to digest proforma which might render the process accessible to lay persons such as myself.  Time is everything.

Thank you again and please feel welcomed at the forum...  I am but a contributor; the forum site is run by an individual who seeks to educate and provide pertinent almanacs and publications common to solving Celestial Navigation observations (reductions).

Respectfully
J**

PS  Please spread your time keeping process to contacts and websites of which you have interest...  I think the concept of democratizing time-keeping is more important than me or any single individual... Most importantly, have fun spreading the word.

[CelNav57]

Matey,

You've done some excellent research work. I edited your post above as the email addresses were not obscured to protect the privacy of both you and the gentleman from Cornell. The hyper link (or whatever it's called) still displayed his and your full email addresses.

Fair winds....

Johannes