Sky & Telescope - September 2021 - 59

ALL PHOTOS COURTESY OF THE AUTHOR
Identifying the ideal location to execute my plan proved
challenging. Roughly 70% of Earth is covered by water, so
most eclipse tracks begin or end above oceans. I instead
searched for an eclipse where the shadow path either began
or ended on or near land. The eclipse of May 10, 2013,
afforded my first opportunity, with totality occurring during
sunrise. Unfortunately, this eclipse was annular rather than
total. Nonetheless, I saw it as a good opportunity to test my
vision. The Moon's antumbral shadow would land in Western
Australia, with a relatively wide path of about 221 km (137
miles). Normally when chasing an eclipse, I'd try to get as
close as possible to the central line. Since the Moon's shadow
was racing from west to east over the Australian desert, it
was easily accessible via the Great Northern Highway 95
that runs north to south. Along this route someone on the
eclipse central line would experience exactly 4 minutes and
4 seconds of annular phase. Unfortunately, I wasn't able to
find any suitable hills to position my model within the proper
line-of-sight at this location.
Through further location scouting, I found an excellent
spot at Radio Hill Lookout in Newman, Australia. This was
near the northern limit of the path of annularity, about 121
km from the central line, which meant that annularity lasted
just 1 minute and 51 seconds. That meant that I'd be sacrificing
133 seconds of annularity, and the lunar silhouette
wouldn't produce a perfect solar ring. No matter - this was
still acceptable for my goal.
I planned to position a couple within the lunar silhouette
so that they would appear to be embracing the ring of fire.
Since the Sun's apparent diameter is about ½°, I had to position
my models approximately 200 meters away so that perspective
would make them appear small enough to be framed
within the ring of annularity.
Displaced Sun
Shooting an event so low in the sky turned out to be a challenging
experience. The eclipse began with the Sun 13.4°
CALCULATING REFRACTION Shooting astronomical targets close
to the horizon requires taking atmospheric refraction into account. Some
nightscape planning apps, as well as the free desktop software Stellarium
(shown above), allow you to input the barometric pressure and
temperature to accurately compensate for the Sun's displacement close
to the horizon.
below the horizon. Just 3 minutes after sunrise, 2nd contact
occurred with the Sun only +0.6° above the horizon. One
minute later the Moon was at its maximum point within the
solar disk, and the Sun's altitude was only +0.8°.
An additional problem I needed to consider when calculating
the shot's precise time and location was atmospheric
refraction. At such a low elevation, the atmosphere that sunlight
was passing through bent the light, displacing the Sun's
apparent altitude. The exact amount of this displacement
varies with barometric pressure and air temperature. Just
above the horizon, atmospheric refraction typically causes the
Sun to appear higher by slightly more than its own diameter.
But at a point only 1° above the horizon, this " lift " is reduced
to slightly less than the Sun's apparent diameter. So taking
refraction into account was very important for my project.
I used the planetarium software Stellarium (stellarium.org),
WITH AND WITHOUT While the image of an annular eclipse at left is impressive, positioning embracing figures within the annular ring inserts a
relatable element to the scene. Through meticulous planning, the author captured Sarah Ponceblan and Gregory Sabatier on a hilltop in Newman,
Australia, as the eclipsed Sun rose over the hilltop on May 10, 2013.
sk yand tele scope .o r g * SEPTEMBER 2021 59

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Sky & Telescope - September 2021

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