COUNTRY SCIENTIST
SOLAR JOURNAL: A recent series of solar aureole images made with the author’s sun occluder.
CAUTION! Always wear sunglasses and
never look at the sun while making aureole
photographs. To avoid sunlight damage to your
camera’s image sensor, you must work fast.
You may void the camera’s warranty if you
damage it by pointing it at the sun.
Doing Science with Your Images
For serious scientific purposes, it’s best to make
solar aureole photos at the same manual settings
(I use 1/1,600 at f4) and at the same time each day
the sun is visible.
Since 1990, I’ve made 2,392 aureole photos at
or near local solar noon. Solar noon varies during
the year, in accordance with the equation of time.
You can find solar noon calculators and tables for
your location online. Just search Google under
“solar noon.” Some sundial sites also have solar
noon tables.
An even better choice would be to photograph the
50 Make: Volume 17
aureole when the sun is at the same angle in the sky.
Again, the web has various sites that provide solar
angle calculators. A good choice would be to select
the sun angle at noon on the winter solstice when
the sun reaches its lowest point in the sky.
Going Further
Next time, we’ll use a free image processing
program to analyze your solar aureole images and
other kinds of photographs.
Forrest M. Mims III ( forrestmims.org), an amateur scientist
and Rolex Award winner, was named one of the “50 Best
Brains in Science” by Discover magazine. His books have sold
more than 7 million copies. He also edits The Citizen Scientist
( sas.org/tcs).
