COMMENT
Dust off your sextant
Captain Michael Howorth muses on how every once in a while it might be good to get back to navigational basics and shoot the sun
I
recently enjoyed the hospitality of a superyacht as she crossed from the Mediterranean to the Caribbean at the start of her winter charter season. For me, it was a wonderful opportunity to get my sea legs back and polish my watchkeeping skills which were in serious danger of going rusty. So, I am particularly grateful to the yacht’s owner, his Captain Sean Read and the crew of the motor yacht, Triumph for the wonderful opportunity of sailing transatlantic.
It was while I was standing the forenoon watch and searching the empty horizon for ships that were not there, that I chanced upon the yacht’s sextant tucked away in a locker on the bridge. A contemporary, lightweight example, it was nowhere near as heavy or as beautifully crafted as the Tamaya I purchased in 1970 when I first qualified as an OOW. But it did the job and I amused myself in shooting the sun and bringing its image down so that its lower limb kissed the horizon 13 miles away. I got the almanac out and worked out the time of Mer Alt, the exact time when the sun reaches its zenith in that latitude. But I didn’t calculate the intercept nor draw the position line on the plotting chart in the fashion I had been taught as a deck cadet sailing in the liners of
the mighty Peninsular and Orient Line all those years ago. The fact is I had forgotten how to do so!
Back in the day before we had electronic navigation, I was used to shooting the sun 5 times during the 8 – 12 watch. I had only my log tables and (if the captain was not looking) my slide rule to do the calculations. We were never allowed to use sight reduction tables for sun shots but did so each morning and evening when shooting stars. Standing on the bridge of Triumph, I was so appalled by my loss of memory and my inability to carry out a task I had done so frequently as a youth that I devoted the rest of my passage sailing towards Antigua using the examples in the front of the almanac and the log tables. By the time we passed
Pidgeon Point and entered Falmouth, I was back to speed and feeling rather proud of myself.
Since the commissioning of the Global Navigation Satellite System (GNSS), its proven accuracy and reliability in all weather conditions have resulted in confidence and almost unquestioning dependence on its ability to provide a vessel’s position, course, and speed. Because of this, its use is widespread, and some seafarers feel that the traditional navigational methods are obsolete. One might ask why ships should still be required to carry navigation equipment and publications.
I amused myself in shooting the sun and bringing its image down so that its lower limb kissed the horizon
The marine environment is a hostile one and failure of electronic equipment is a constant possibility. Currently solar activity is increasing with the possibility of severe solar storms affecting GNSS accuracy or damaging satellites. The possibility of such failure should ensure that no prudent seafarer would proceed on an ocean passage without a reliable navigational back-up.
Since J W Norie published the first edition of his Complete Set of Nautical Tables and Epitome of Practical Navigation in 1803, many changes to the tables
have been necessary in both content and presentation. New tables have been included, obsolete ones deleted to conform with changing techniques of navigation, with the aim of improving the accuracy of the calculated position and reducing the tedium of the calculation.
Norie still publish these tables and they do so because one day you might – just might – have need of them. So next time you have a spare moment when out at sea, dust off the sextant and keep your hand in. If you can’t remember how to do it, find an old fart like me and ask him if he would like to sail across the Atlantic and show the deckies how it is done. I would jump at the chance to do it again!
ONBOARD | SPRING 2023 | 5
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