A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Bob Goethe
Date: 2018 Mar 9, 18:30 -0800
If you are a time junkie like me, you have discovered that you can listen to the shortwave radio station WWV and get the UTC time...and that the pattern of double-ticks right after the top of the minute tell you the difference between UTC and UT1. Right now, UTC is 0.2 seconds slow compared to UT1.
I just now discovered that if you dig deep into the NIST web site, you can find one (and only one) time server that delivers time in terms of UT1 rather than UTC. The server is:
I went into the regedit program of my Windows 10 computer and got to this key: Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\DateTime\Servers
I added a string value item to the right hand pane of the window, and added the UT1 server, as illustrated in the attached photo. This let me go in through the Control Panel >> Clock, Language & Region >> Date & Time >> Internet Time >> Settings, and find that the UT1 server was now available in my list. I chose it, and then hit the "Update Now" button.
But more to the point for taking sextant shots, I also went to my Android cellphone, where I have an app called "ClockSync" which displays my phone's system time, "atomic time", and the offset between them. In the settings menu, I was able to change its time server as well.
I am aware there are going to be network irregularities and delays that could amount to more than the 0.2 second difference between UTC and UT1, but at least I am doing what I can.
Being, as I say, a time junkie, I have both a Casio WaveCeptor radio controlled watch, and a $25 shortwave radio that is smaller than a paperback book. Right this moment, the watch and station WWV as so close together that I cannot distinguish an offset between them. However, this has let me calibrate the "Atomic Time" display (now set to UT1/GMT) on my cellphone, so to speak, and I see that it is a tiny bit faster - not by much, but by enough to observe - than my watch. So at least on this occasion, the "ClockSync" app has done as good a job of setting my phone to UT1 as I can verify by eye.
Does it matter practically to me in my sextant shots? Not at all. Do I feel gratified to know I have this sort of precision now available to me? Absolutely.