The Nocturnal -- How we told the time at night before mechanical clocks

3. Before
we had
these….

4. …we used these.
Which was fine,
until this
happened:

5. After sunset, your
timekeeping options became
limited. You may ask how
important it was to keep time
after dark in pre-industrial
society. It was very
important to at least one
group of people:

6. Early sailors could predict the tides by observing
lunar cycles, but predictions were worthless
without an accurate measure of time. This was
critical to avoid running aground at low tide or
trying to sail against tidal currents.

7. Why is my
animated .GIF not
displaying in
powerpoint
online? It works
fine offline on my
laptop.
Cross platform…
Won’t work in
Firefox, Edge or
Android. Wassup
wit dat?
At least the auto
update feature
seems to work.
Refresh the page
and my edits
magically appear.
The second had
sweep on this
cheap Rolex
knockoff is
supposed to be
ticking along, yet
PowerPoint online
refuses to display
animated .GIFs

8. And this star field is
supposed to be rotating
about Polaris.

9. Raymon Llull 1232 - 1315
Horologium Nocturnum
The Latin name for what
became known as the
Nocturnal. Here are a few
early examples ranging
from simple to intricate.
13th century Catalonian scholar was the first to
leave a written record describing the Nocturnal.

10. Compassrosegeocoin.com Bronze Nocturnal
$29.94 – out of stock
Shepherdswatch.com
Pewter Nocturnal
Pendant
$40.00
Nocturnals were commonly used for nearly 500 years before they gave way to mechanical clocks. Today only a few
examples of commercially produced nocturnals survive. (This is not an advertisement or endorsement of these
products, they are shown for educational purposes only.)

11. Sky & Telescope DIY Star Clock
Free download at:
https://www.skyandtelescope.com/astronomy-resources/make-a-star-clock/
Fortunately it’s not too difficult or expensive to make your own nocturnal.
The Sky & Telescope version isn’t too precise, but it’s user friendly.

12. Instructables.com
Nocturnal Celestial Stardial
Free PDF download at:
https://www.instructables.c
om/id/2d-Nocturnal-
Celestial-Stardial-TJT16/
Here’s my favorite. Tried and
tested, I can tell the time at night
within 5 or 10 minutes.
Of course, if the purple isn’t your
color...

13. ….it’s available in a few other lovely color schemes….

14. Including my
personal
favorite:
Grayscale
Download the free PDF,
print it on heavy card
stock. It’s worth having
your print laminated at an
office supply store. Cut
out the three pieces and
assemble.

15. The instructions recommend using a rivet or eyelet for the pivot. I
used a grommet setter (Harbor Freight <$5) which gives you a nice
wide center hole to line up the North Star.

16. Here’s my assemble version
printed on heavy card stock.
I recommend laminating for
stiffness, durability, and
protection from the
elements.

17. The outer scale is divided into months. Day graduations
are in 5 day steps for ease and accuracy of alignment.

18. Dial (B) has three tabs, one for
each of the reference
constellations.
The time scale is graduated in
hours with 10 and 5 minute
increments.

19. Stellarium Simulation -- Aurora, Colorado
March 17, 2019 22:00 MDT
Locate Polaris, the North Star.

20. Here’s a little help if you’re
having trouble! The pointer
stars are highlighted and
noted. Decide which of the
reference constellations is
highest above Polaris from
your perspective.

21. Find the tab for the
constellation you chose.
Align the straight edge of
that tab with today’s date.
In this example we are
using March 17. Best
accomplished by
candlelight or some form or
artificial illumination.

22. Once again face North and locate Polaris.

23. Hold the nocturnal in
front of you at arms
length. Try to keep it
vertical while you align
Polaris through the
center hole.
Rotate dial (A) until it
points at your target
star, in this case the
pointer stars of the Big
Dipper asterism.

24. Return to your candlelight and read
the time where the straight edge of
dial (A) intersects the inner scale.
This example shows 9:00 PM. Add
1 hour for Daylight Time and you
get 10:00 PM, exactly what the
Stellarium simulation shows.