Photo of snowy Sussex woodland trail Photo of snowy Sussex woodland trail

The Future of Celestial Navigation

Tristan Gooley

A morning glance at a moody and cloudy twilight led me to laying down some of my thoughts about the key challenges facing celestial navigation and how my natural navigation experience – using no instruments at all – relates to it. The differences lie more in philosophy than fundamentals.


Celestial navigation is a lot more restrictive than most people who are new to the subject imagine. Like a lot of others, I had a lofty and romantic notion before picking up a sextant for the first time. I saw myself putting down my digestif and leisurely reaching for a brass instrument in the middle of the night.

The truth is that using a sextant, for navigation rather than curiosity, is rarely leisurely. Often it can be a near frantic business, particularly if the holder of the sextant has other responsibilities, like skippering a boat. The need for speed is because of the need for a horizon.

The sextant is just one of the latest steps in the history of measuring angles, specifically the angle between a celestial object like a star, planet, sun or moon, and the horizon.

Its many ancestors include the quadrant, backstaff and kamal. It is this need for a horizon that adds a time pressure and tears up any laid-back approaches.

Star sights still have to be taken when a horizon is clearly visible and there is only one period of time when both the stars and the horizon are clearly visible, it occurs twice in each 24 hour period, and it is called ‘twilight’.

Twilight is slippery, one minute we are squinting into a western horizon, stars far from our mind, the next it is dark, the stars rule the upper demisphere and the horizon has dissolved into the water.

(Arguably the easiest and most popular celestial navigation sight does not require twilight, but then time becomes even more critical. The noon sight must catch the midday sun at its zenith. This only lasts a second and the whole point of the sight is that we never know exactly which second it will be – we would have no need for the sight if we did because we would already know our position. This means that the few minutes around local apparent noon are an intense and busy time for the celestial navigator.)

How does this all differ from natural navigation? Well, as I pointed out earlier, it is largely a philosophical difference. Celestial navigation evolved as an accurate means, when used in tandem with dead reckoning, of primary navigation. In the age before GPS (technically I should write GNSS – Global Navigation Satellite System) celestial navigation was the best method of accurately plotting a position mid-ocean.

Natural navigation, in the context that I research, write and teach at least, is an art and science that has been reborn in a GPS age. Its roots predate GPS and sextant navigation by thousands of years, but it had largely died a death and so its rebirth has given it an advantage. It does not need pinpoint accuracy, it is more about understanding a journey than avoiding rocky lee shores. Used sensibly in conjunction with all other navigation methods such as GPS, compass and chart, it does add a small layer of safety because it can help spot and check for gross error. Land-based satellite navigators are forever appearing in the news as they drive their cars to cliff edges, whilst blindly obeying a SatNav command. This sort of calamity is a lot less likely if the driver, skipper or pilot, is tuned to their natural surroundings. Even so, that is still not its main raison d’etre in the modern age, from my perspective.

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 practising 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 the its role in improving understanding and awareness.

This has been happening by stealth and in a quiet way for years now, but it is not something for the sextant community to be ashamed of. It is an opportunity.

For more on celestial navigation, please see the book How to Read Water. It has a section about celestial navigation that I’m quite proud of.