SKY_September2014.pdf

(^) The Moon • September 2014
Howard Eskildsen
Amateur astronomer Howard Eskildsen can often be found observing the Sun and
Moon from his home in Ocala, Florida.
September 7 8
9
10
-K bands of a spectroheliograph to produce
the fi rst photographs of solar prominences
taken when the Sun was not in eclipse.
Although prominences are distinctly vis-
ible in Ca-K, they aren’t as bright as when
seen in Hα light, and to image them you’ll
need to increase the camera’s exposure to
the point of overexposing the solar disk.
Prominences appear in many diff erent
forms, such as jets, plumes, loops, and
hedgerows. They may hover close to the
solar limb or may extend tens of thousands
of kilometers beyond the chromosphere.
At fi rst glance they appear stationary in
space, but over several minutes promi-
nences often reveal surprising changes in
shape and size. You might see fi laments of
plasma streaming through the prominence
or raining back down onto the Sun.
There are many options available for
the solar observer to get in on this K-line
action. These include dedicated solar
scopes as well as specially designed fi lters
that you can add to most refractors. Also, a
wide range of high-quality video cameras
are readily available at reasonable prices. I
suggest a monochrome camera, because
you’ll be catching only a thin slice of the
violet spectrum. Avoid color cameras
for this work, because these models use
built-in fi lters to generate a color image,
and these fi lters often block the violet end
Sunspots appear very similar in Ca-K light as
they do in white light. This similarity includes the
dark umbral and lighter penumbral regions. But
in Ca-K these features are always surrounded by
bright plages connected to the intense magnetic
fi elds associated with sunspots.
Librations
Kircher (crater) September 7
Schomberger (crater) September 8
Mare Australe September 9
Phillips (crater) September 10
Distances
Perigee September 8, 4h UT
222,692 miles diam. 33′ 20 ′′
Apogee September 20, 14h UT
252,180 miles diam. 29′ 26 ′′
FIRST QUARTER
September 2, 11:11 UT
FULL MOON
September 9, 1:38 UT
FIRST QUARTER
September 16, 2:05 UT
NEW MOON
September 24, 6:14 UT
Phases
For key dates, black dots on the map
indicate what part of the Moon’s limb
is tipped the most toward Earth by
libration under favorable illumination.
S&T: DENNIS DI CICCO
HOWARD ESKILDSEN (2)
of the spectrum. My solar setup consists
of an Orion ED80 80-mm f/7.5 refractor
with a Lunt Solar Systems B600 calcium
K-line fi lter, and an Imaging Source DMK
41AF02.AS monochrome video camera
connected to a laptop computer to display
and record images.
For all that Ca-K has to off er, it’s unfor-
tunate that this purple Sun is so diffi cult
to see visually. But with the help of a cam-
era and monitor, anyone can see this excit-
ing world of continuous solar action. ✦
Because some observers’ eyes are not sensi-
tive to near-ultraviolet wavelengths, it’s easiest
to share the view with others using a video
camera, laptop computer, and a dark covering to
shade the computer screen.
Magnetic
reconnection events
Plages
Sunspots
Old, deteriorating plages
SkyandTelescope.com September 2014 55
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