Making a CD-Sextant
by Paul C
Now that the stars are out later in the morning,
and the boats are all put away, it’s time to think of
winter projects that will keep us busy.
I am a “land locked” sailor, mostly confined to
Michigan’s inland lakes, navigating the oceans has always
intrigued me. And, while I no longer see quite the allure of
Tahiti, exploring the Caribbean is still a “goal”
that is out there! To properly cruise the Caribbean, one really
needs to know how to navigate. As a kid growing up, we read
the adventures of Hornblower. When a midshipman, he was taught
the seamanlike skills, of which navigating was a significant
part. The tales of Hornblower and his fellow messmates made
navigation seem a truly difficult art.
On the flip side, we also grew up with a copy
of Chapman’s “Piloting, Seamanship, and Small Boat
Handling” for rainy-day reading. This provided a background
for the theory of navigation, but I had no chance for experience.
Later years brought “Safe Boating” classes that
discussed navigation only briefly while spending much more time
on the Rules of the Road, Lights, Buoys, and the like (all very
important too!). Alas, any serious attempt to learn navigation
was always stymied by the lack of a sextant. When raising four
kids, a sextant was a luxury that did not fit the practical
budget. Building small boats was a stretch on the budget as
it was. Finally all of this has changed! This year I found the
plans for the CD-Sextant. And where else, but on the Internet!
The plans are detailed but construction is really
straightforward. Now for the accumulation of the necessary parts.
Small mirrors are difficult to find. A trip to
Walgreens yielded a Maybelline compact on the “sale item”
shelf. The college girl clerk did look at me funny when I explained
what I was looking for and how I planned to use it. Upon returning
home, heating the plastic housing ultimately loosened the glue
which allowed the mirror to pop out.
Construction went smoothly. The most difficult
part being breaking the mirror in half and then the removal
of the silvered portion from one half of that half. The line
in the instructions regarding the slow scraping with a razor
blade removed the silver nicely. If you are under 18, have an
adult do it for you. The balance of the construction was very
straightforward. Thankfully we still have a Lego bin at our
house! Certainly small blocks of wood could easily have replaced
I used an exposed x-ray as the sun shield. I am
not sure if this is particularly ideal since after all we are
looking at the Sun! (All Standard Disclaimers!!! Don’t
look at the sun. X-ray film is not an adequate filter! Looking
at the sun DOES cause blindness!) Use this sextant to look at
the moon and the stars! This is a cool instrument that does
I am again a navigation student learning to use
my sextant. I feel like the midshipmen mentioned above. Of course
taking the sights from the same landlocked location does take
some of the challenge out it. Besides the “deck”
is not pitching. And it’s not like the consequences of
being unable to verify your reading if we were out on the open
sea. But, since I am being self taught, as long as I keep finding
myself still at latitude 43 degrees, I guess I am doing it right!
I continue taking sights on different objects at varying times
of the day and night for practice (and fun). This brings me
another step closer to being able to go to sea!
There are numerous freeware and shareware navigation
computer programs available to assist with the astronomical
tables and the “navigation math.” While in the purist
sense, this is cheating, it is also very helpful when you are
being self taught. Do a Google ™ search on “Navigation
+ Freeware” and “Navigation + Shareware.”
Bowditch is another excellent source of traditional navigation
instruction. Hopefully a copy can be found at your public library.
This is a fun, practical and not particularly
complicated project. Done step by step, it goes very smoothly.
Plans are at: “The
CD-Sextant Build Your Own Sextant.” I would
like to thank the author for his creative offering!
Try it out on your next rainy day!