Sky & Telescope - October 2019 - 22

The H-Alpha Sky

deep Hα image of the entire night sky. It began not as a grand
plan, but rather an evolution of the skills and common interests of three astrophotography friends - David Mittelman,
myself, and Sean Walker (hence the MDW in the survey's
name).
Soon after Sean joined the Sky & Telescope staff in 2000, he
and I began working on a variety of imaging projects involving deep Hα images made from my backyard observatory in
Boston's western suburbs. As the chips in affordable CCD
cameras grew larger, we began experimenting with a branch
of astrophotography that had long interested both of us -
wide-angle imaging done with camera lenses.
One ambitious project involved trying to capture any portion of the enormous but faint western edge of the OrionEridanus Superbubble, an emission feature almost unknown
to amateur astrophotographers at the time. Success came on
the ﬁrst night. As our exposures made on subsequent nights
panned haphazardly outward searching for the limits of what
we could image, Sean began piecing the results together into
a mosaic. With a few extra shots to ﬁll in missing sections
of the superbubble, the result proved interesting enough to
appear as a story on wide-ﬁeld imaging in this magazine's
April 2009 issue, page 66.
Our next project was a more carefully planned mosaic of
the Milky Way stretching from Puppis to Perseus. Made using
a 110-mm camera lens, it covered more than 7,000 square
degrees of sky with a resolution of about 17 arcseconds per
pixel. The following year we made deeper mosaics of selected
regions in this ﬁeld using a 100-mm f/4 astrograph that
increased the resolution to better than 5 arcseconds per pixel.
Around this time, and through overlapping circles of
mutual friends, we connected with David Mittelman, who
had a passion for astronomy dating to his days as a science
major at Middlebury College. He had recently installed a
pair of remotely operated telescopes at New Mexico Skies
(nmskies.com). Most weeks the three of us would get
together for an evening of talking shop and processing some
of the latest images from the New Mexico scopes.
Dave became increasingly fascinated with the mosaics Sean and I were working on, including a new one of the
Cygnus region made at a resolution of about 3 arcseconds
per pixel. The resulting deep Hα image provided a dramatically new look at one of the sky's most targeted areas for
wide-angle photographs. Not surprisingly, our conversations
turned to what it would be like to photograph the entire
(continued on page 26)
t Top: Located 15° southwest of the Veil Nebula, the supernova remnant G70.0-21.5 is larger than the Veil, but virtually unknown because it
is so much fainter. This 8°-wide field straddles the Pegasus/Vulpecula
border. The bright star in the field is 1 Pegasi. Middle: The Milky Way
running from Auriga at lower left to the well-known Heart Nebula (IC
1805) in Cassiopeia at right contains many moderately bright emission
features overlooked by astrophotographers. Bottom: Among the sky's
most photographed deep-sky objects, the Veil Nebula in Cygnus is surrounded by fainter clouds of glowing hydrogen. The field is 14° wide.

OCTOBE R 2 019 * SK Y & TELESCOPE

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Sky & Telescope - October 2019

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