Use of Celestial Navigation Today

I kind of like it, tbh, but most Rotterdam is a pretty… “industrial” place from my trips through there. This has got some pizzazz!

This “compass” works perfectly… if the watch shows noon at the true local noon.

The Equation of Time is not the problem, through the year the difference is only about ±15 minutes.

The time zones (and in addition the daylight time) matter much more:
From Cape Finisterre, the westernmost point of Spain, to Otranto, the Italian side of the entry into the Adriatic Sea, or to the eastern part of Hungary, the true local noon varies by two hours in the same time zone.
In higher latitudes, this is extreme: Inside Norway alone; the true noon varies by nearly two hours


A post was split to a new topic: Opinion | Ditch the GPS. It’s ruining your brain. - WP

It’s possible in navigation theory to get deep in the weeds. To help guys like us that have to solve problems on a practical level rules of thumb are used. Like the fix in the middle of the triangle. Simple and close enough.

We’ve heard don’t rely on any single aid, particularly a floating aid a million times. GPS is a different kettle of fish however. Can’t be evaluated with simple rules.

With sophisticated systems using independent verification used in the offshore industry it is impossible to spoof the GPS signal and have it pass unnoticed. If the GPS signals disappeared altogether world wide it may be a good time to pucker up and kiss your fufu valve goodbye because nothing good is happening.
If knowledge is allowed to pass from the instructor to pupil without rigour then that knowledge slowly degrades. We need the instructor to get among the weeds to lift and maintain the standards and it is not just in Navigation. There has been catastrophic failures in the operation of the main engine of a large container ship and serious damage to the switch board of a cruise ship that I’m aware of. Both cases had the senior officers who commissioned the vessel having been relieved by other officers and then these officers passing the knowledge down to others until it became like Chinese whispers and vital information was lost.


Yes, well put. I thought this tread: Interesting Article - How Technology Grows was relevant to marine engineering in the sense of having deep understanding vs work-a-day knowledge.

When I was sailing international in the 1970’s & 1980’s, I would sometimes come across a ship in the middle of the ocean flashing some kind of Morse Code at me. I have never been able to remember Morse Code so I would simply call on VHF 16 and ask them what they want. It was always somebody just wanting to practice.

I was once part of a riding crew on a tug being towed by an AHTS from Morgan City to Bombay, India. I would perform my Cel Nav every day & night and then compare my position to the position obtained by the AHTS’s Captain, a retired US Navy Commander. We usually got between 5 to 10 miles within each other, sometimes a little closer. Keep in mind that we were separated by only 1,800 feet of tow wire!


CELNAV is actually a thing. It can be completely automated and computer driven, coordinated with NMEA networks to control and helm systems. More costly than standard equipment, can be integrated into commercial navigation systems.

7 posts were split to a new topic: Lunar Distance and other From 1883 Ed of Bowditch

I was taught to not bother with LAN, just shoot a regular LOP around noon and be done with it. With modern calculators it’s actually easier to reduce a normal sun line anyway.

could see that. In the days of tables, LAN was a much much easier calculation. Spent a few months in Antarctica and we got to shoot LAM ( local apparent midnight )

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Don’t really want to revive this thread to but I’ll put is this way.

If you were put in charge of risk assessment for say 1000 ships, bulkers, tankers, container ships, RO/RO and so forth would your first memo to the fleet be that you wanted everyone to start practicing celestial in case the GPS failed?

If I was down in the trenches on a big RO/RO in shitty weather trying to slog my way though a coast-wise without killing someone I’d think that the person who sent that memo was an idiot.

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CelNav is the equivalent of throwing a log tied to a knotted line off the stern to measure your speed, (You never know when the Doppler might break!) or lead lines (never know when the Fathometer might break!), or Morse over flashing light (the radio might break!), or sails (the engines might break!), or timber raft building (the ship could sink!).

I enjoy CelNav. I enjoy baffling the kids with stuff they don’t learn in school (lunars, double altitudes, deriving longitude by moonrise without a clock). I also know these skills are oddities of a bygone time that are as likely to help me as an astrolabe.

while I agree in principal - I think it is still important for officers to be able to evaluate what is happening without being overly reliant on electronics. Watching movement of bubbles, ect alongside is still useful to see movement at slow speeds, looking for, and using natural ranges on anchor watch to check for dragging, bearing drift - nut just over the compass - but out the window, and many others. Cel Nav IMO is part of that same mind set that is just part of a healthy skepticism of electronics and an ability to confidently navigate the vessel without them.

As an example, years ago I boarded a vessel, at anchor that my company had on charter and which we believed to be aground, as an observer for our interests. The Captain insisted he was not aground and kept pointing to his electronic chart. My simple question back was, Capt if you are not aground, why are you pointing in a different direction than all the other ships at anchor.


I agree with the general mindset you’re describing here, a kind of total, constant awareness to the situation, the ship, environmental factors and so forth. But I think celnav has limited value here because unlike the bearings of landmarks or weather conditions, things that can be directly observed, reducing sights has too many steps in the process to be usable in that way.

Plugging the daily position into a spreadsheet yields useful information, days run and so forth but it’s not the same as the way a ship feels in a turn.

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“reducing sights has too many steps in the process”. There is an App for that! DR from that thumbprint on the chart while you fire up your version of a PPU with the BT GPS that reads all navigation satellites not just one system. That fails then it’s time for the sun gun. You may have to change Apps.


I’ve come across a couple of items about this which deserve a new thread but here is one from a professional writer, Tristen Gooley that exactly nails what I’ve been trying to get across, also the point @texastanker makes in his post:

The Future of Celestial Navigation

The saddest thing for celestial navigation is the way it is taught these days – if it is taught at all. I learnt through the RYA Ocean Yachtmaster course. It is effective in many ways, but the celestial navigation part (by far the lion’s share of a 5 day course) did not improve my understanding of the natural world one iota. It is such a great pity that the subject is so often presented as being about Greenwich Hour Angles and error corrections. When I teach natural navigation it is about the earth, the moon, the sun and the stars. I will happily concede that someone using conventional celestial navigation can get a more accurate fix than the hands-free navigator. However, their understanding of what is happening around them and its beautiful interconnections and interplay, may not compare.

This is the key difference and celestial navigation’s Achilles heel in the modern navigation environment. It is a technical business that uses an instrument and requires practiced skills, but for all that it does not rival more modern instruments for accuracy. I would encourage those who treasure celestial navigation and enjoy practicing it, as I do from time to time, to consider changing the way it is taught, portrayed and defended. I am convinced that its future would be more secure if its proponents surrendered some of the high ground of claiming its necessity and instead championed its role in improving understanding and awareness


My brain really likes understanding WHY as opposed to just learning the procedures for how to get an answer. The problem is that celestial is a complicated topic and takes an entire semester at an academy just to teach the lowest common denominator the basic procedure how to get a fix. I had the opportunity to take an elective course, Celestial Navigation II, which was basically all the theory behind it and loved it, but some people really struggle with that kind of stuff.

It’s a bit like my experience with the the magnetic compass. After three months tangling with Weber metres and formulas I can barely remember existing, including formulas for susceptibility, we were finally granted a look at a magnetic compass. Unfortunately the magnetic compass was mounted on a deviascope. An instrument of torture where the candidate, us, played around with tiny magnets under the gaze of the examiner, and tried to explain our reasons for each action we took.
Practical swinging of a ships compass at the end of the course was by contrast, enjoyable.

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