Astronomy

Saturn’s
phantom spokes
appear as bright
radial lines
reaching out
across the
planet’s rings. NASA/
JPL/SPACE SCIENCE INSTITUTE
(TOP); CASSINI IMAGING TEAM,
ISS, JPL, ESA, NASA (BOTTOM
IMAGES)
The ringed
planet saw seasons
change for billions
of years before
NASA’s Cassini
spacecraft caught
this first shot of
saturnian equinox.
NASA/JPL/SPACE SCIENCE
INSTITUTE (OPENING SPREAD)
eagle-eyed observer
results with photometric observations he
was taking with a 16-inch reflector at
Harvard’s remote Oak Ridge Observatory.
Considering my routine brightness estimates
of variable stars to within 0.1 magnitude,
I told him it might be possible and
was eager to try.
Observing lessons
I started by observing Saturn through
an eyepiece that yielded 125x. I thought I
could maximize my chances of success by
condensing the light of the A ring, which
would make any brightness differences
more noticeable. But I abandoned the
search because light from the B ring overpowered
the view. I also realized that trying
to search for “possible” 0.1-magnitude
differences across a single expanse of light
was different from comparing a variable
star of unknown brightness to different
point sources of known brightness.
I had to rethink my strategy. Because
Saturn was high in the sky after sunset,
I decided to start observing as soon as it
became visible in the twilight. This doublestar
observing technique would reduce the
contrast between the A and B rings, allowing
me a better view. I also selected an
8.4mm Fecker eyepiece (a simple design
combining two lenses) that provided a narrow
field of view (10') and a magnification
of 327x through the 9-inch refractor. In
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