Time Precision Needed for Celestial

[Dockhead]

My best sailing friend studied astrophysics as an underground and is a master of celestial nav. I'm hoping to not be too busy the next time we cross an ocean together to take his classes.


I think with the widespread jamming and disruption of GPS we are seeing these days, these skills are more relevant than they were before. I note that the US Navy has re-introduced celestial nav.



Meanwhile I was thinking about how to solve the time problem in a robust way, so that you can do celestial even after a bad lightning strike etc. which wipes out your electronics.


I was discouraged to find out that mechanical chronometers are exorbitantly expensive to service and adjust.


So I'm looking at quartz marine chronometers, like the Seiko QM-10 and QM-11, which is not that expensive and readily available.



It has electronics so would be vulnerable to EMP but maybe could simply be kept in a metal box.


The accuracy looks like 60 seconds a year, but I don't know how crystal aging affects that -- these are decades old by now.



I also don't know if that's accurate enough -- 5 seconds a month?


There are HAQ watches available which are accurate to 10 seconds a year or even 5 seconds a year, which I guess could likewise be kept in a metal box.


Or maybe it's not all that important if you reset it to GPS time once a week.


With that process, maybe even a mechanical one would be OK.


Views?

[GordMay]

Originally Posted by Dockhead

...
I think with the widespread jamming and disruption of GPS we are seeing these days, these skills are more relevant than they were before. I note that the US Navy has re-introduced celestial nav. ...

“Global navigation jamming will only get worse. The U.S. needs to move fast” ~ by Sean Gorman
➥ https://spacenews.com/global-navigat...eds-move-fast/

“Jamming and spoofing attacks on GPS, and other global navigation satellite systems [GNSS], are becoming increasingly common, as geopolitical crises escalate, creating major challenges and risks for aviation, shipping, and other critical services, across the world.

Data, from GPSJam.org*, has confirmed widespread GPS/GNSS interference, across parts of Europe, and beyond, as an outcome of the war in Ukraine.

Regions affected range from Finland and the Baltics, to Poland, Romania and Bulgaria; in addition to the Black Sea, the Caucasus, and Turkey.
The Middle East is also being affected by interference, stemming from Israel and Iran’s hostile activities, in the region.
Other interference efforts, albeit at a lower scale, are also regularly occurring in areas of Pakistan, India, and Myanmar...”

* GPSJAM: Daily maps of GPS interference ➥ https://gpsjam.org/
FAQ ➥ https://gpsjam.org/faq

[Mal Reynolds]

Any quartz device will do (Casio), and digital more accurate than analog.

Earth rotates at 465.1 m/s at the equator or about 1/4 nm/sec.

Pre-gps we set the time by the time signal at WWV https://www.nist.gov/pml/time-and-fr...io-station-wwv

In case of the zombie apocalypse, Citizen has an HAQ solar version so you don't have to worry about a battery.

Your cocked hat size will most likely be driven by sea-state.

[GordMay]

The future of Global Navigation Satellite Systems [GNSS] may lie in a combined use of GPS and Galileo [and, perhaps, GLONASS, & Beidou]. A multi-mode system, with a second or [3RD or 4TH] constellation, effectively eliminates any common modes of failure, with GPS, improving dependability by a factor of 1,000, or more.

[carstenb]

Originally Posted by Dockhead

My best sailing friend studied astrophysics as an underground and is a master of celestial nav. I'm hoping to not be too busy the next time we cross an ocean together to take his classes.


I think with the widespread jamming and disruption of GPS we are seeing these days, these skills are more relevant than they were before. I note that the US Navy has re-introduced celestial nav.



Meanwhile I was thinking about how to solve the time problem in a robust way, so that you can do celestial even after a bad lightning strike etc. which wipes out your electronics.


I was discouraged to find out that mechanical chronometers are exorbitantly expensive to service and adjust.


So I'm looking at quartz marine chronometers, like the Seiko QM-10 and QM-11, which is not that expensive and readily available.



It has electronics so would be vulnerable to EMP but maybe could simply be kept in a metal box.


The accuracy looks like 60 seconds a year, but I don't know how crystal aging affects that -- these are decades old by now.



I also don't know if that's accurate enough -- 5 seconds a month?


There are HAQ watches available which are accurate to 10 seconds a year or even 5 seconds a year, which I guess could likewise be kept in a metal box.


Or maybe it's not all that important if you reset it to GPS time once a week.


With that process, maybe even a mechanical one would be OK.


Views?

Dockhead - if I recall correctly, you have an old US Destroyer clock (such as the one I have) hanging in
your salon. I would suggest if it was good enough for them during WWII to find their position, then its accuracy is probably also good enough for you. Just make sure it is serviced and adjusted regularly

[s/v Jedi]

Originally Posted by GordMay

The future of Global Navigation Satellite Systems [GNSS] may lie in a combined use of GPS and Galileo [and, perhaps, GLONASS, & Beidou]. A multi-mode system, with a second or [3RD or 4TH] constellation, effectively eliminates any common modes of failure, with GPS, improving dependability by a factor of 1,000, or more.

We use GPS + GLONASS simultaneously at all times and some sensors can use Galileo as a third constellation but I’m not even sure of it’s status anymore.

But for electronic warfare I think they are all taken out in one flip of the switch