Sky and Telescope - August 2017 - 20

FILMING TOTALITY

by Hugh Hudson & Mark Bender

The
Eclipse
Megamovie
Project
Join a citizen-science campaign on August 21st to
record 90 minutes of the Sun's changing corona.

A U G U S T 2 0 1 7 * SK Y & TELESCOPE

p BUTTERFLY AT MINIMUM This photo of the March 29, 2006, eclipse
shows the solar corona as it looked one sunspot cycle ago. During this last
quiet period of solar activity, the corona appeared more extended at the
equator than at the poles. The 2017 corona will likely present similarly.

as this one, the coronal magnetic ﬁeld resembles that of a
simple - but truly colossal - bar magnet. Inside the Sun this
ﬁeld periodically develops twists and kinks that cause sunspots and other magnetic activity to come and go every 11
years in a (mostly) predictable cycle. How will the corona of
2017 compare to the corona one cycle before, as seen above?

Our Plan
The Eclipse Megamovie Project hopes to enlist more than
1,000 volunteers, each armed with digital single-lens reﬂex
cameras (DSLRs), telephoto lenses, and tripods to help
unravel these scientiﬁc mysteries. The project will stitch
together a near-continuous view of totality as the eclipse
crosses the country from northwest to southeast. GPS metadata is also desirable for the DSLRs; see https://eclipsemega.
movie for up-to-date information about equipment and
arrangements. Relatively quickly after the eclipse, depending
on volunteers' connectivity, an algorithm will stitch together
thousands of photographers' images into a movie that spans
the full 90 minutes the eclipse spent over land.
However, the core of the Megamovie Project will not be
the immediate movie, but the archive of all the observations,
taken from many different sources and having many differ-

ECLIPSE: LORENZO CO M OLLI & A LESSA NDRO G A MBA RO

the "Eclipse Across America" rushes toward us,
how can we best use such a wonderful opportunity? With totality traveling across the continental
U.S. for a full 90 minutes, it will be the longest and bestobserved total solar eclipse of the digital era. Watchers will
have tools that could hardly have been imagined in 1918, the
year of the last cross-country total eclipse in the U.S. For the
ﬁrst time we'll have a chance to record vast numbers of images
that continuously track the spectacle from coast to coast.
These images will not just be pretty mementos. A big
part of totality's beauty is the Sun's wispy outer atmosphere,
the corona. Its delicate tendrils create a breathtaking aura
around the blacked-out Sun. Since the corona's appearance
changes with time, observers across North America will see
slightly different views from their different perspectives.
The corona, much hotter than the Sun's visible surface, is
full of waves and ﬂows that are rooted in the Sun's magnetic
activity. One key to understanding these ephemeral mysteries
lies in time sequences of high-quality images. After eclipse day,
we should have many thousands of consecutive glimpses of the
corona as it evolves through the long totality - a time when
the Moon acts as a celestial parasol, blocking out the bright
solar disk and enabling us to see deeper into the seething atmosphere than is possible from Earth at any other time. Nobody
has seen coronal motions with such time resolution before.
Variability in the corona will also show us the subtle evolution of our star's "magnetic skeleton," which dictates the
shapes that we see. During years of low solar activity, such

https://eclipsemega.movie https://eclipsemega.movie

Sky and Telescope - August 2017

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