ONBOARD Magazine - spring 2023

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
I amused myself in
shooting the sun and
bringing its image down
so that its lower limb
kissed the horizon
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.
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