http://science.nasa.gov/headlines/y2009/19feb_quadrupletransit.htm

Spectacular Photo-op on Saturn
NASA Science News
02.19.2009

February 19, 2009: Something is about to happen on Saturn that's so
pretty, even Hubble will pause to take a look.

"On Feb. 24th, there's going to be a quadruple transit of Saturn's
moons," says Keith Noll of the Hubble Space Telescope Science
Institute.
"Titan, Mimas, Dione and Enceladus will pass directly in front of
Saturn
and we'll see their silhouettes crossing Saturn's cloudtopsâall four
at
the same time."

Hubble won't be the only one looking. Amateur astronomers will be able
to see it, too. The timing favors observers along the Pacific coast of
North America, Alaska, Hawaii, Australia and east Asia.

On Feb. 8th, astrophotographer Christopher Go of the Philippines got a
preview when Titan transited Saturn all by itself. He recorded this
movie using an 11-inch telescope:

http://science.nasa.gov/headlines/y2009/images/quadrupletransit/
Christopher-Go2.jpg>

Above: Titan transits Saturn on Feb. 8, 2009. Credit: Christopher Go
of
Cebu City, the Philippines.

"I woke up at one o'clock in the morning to photograph Titan's passage
across the disk of Saturn," says Go. "The sky was overcast, but I was
fortunate to see the end of the transit through a break in the clouds.
The emergence of Titan was really stunning because it gave the moon a
3D
appearance!"

Transits like these are rare. "They only happen every 14 to 15 years
when the orbits of Saturn's moons are nearly edge-on to Earth," says
Noll. In 1995-96, the last time the geometry was right, Hubble
photographed two (Titan and Tethys) and three (Mimas, Enceladus,
Dione)
moons transiting Saturn. This will be the first time the great
telescope
captures four.

The event begins on Tuesday morning, Feb. 24th at 10:54 UT (2:54 a.m.
PST) when Titan's circular shadow falls across Saturn's cloudtops.
About
forty minutes later, the ruddy disk of Titan itself moves over the
clouds.

"Titan is so big, you can see it just by looking through the eyepiece
of
a small telescopeâno special camera is required," says Go.

One by one, the smaller moons Mimas, Dione and Enceladus will follow
Titan. At 14:24 UT, all four satellites and their shadows will
simultaneously dot Saturn's disk: animation
http://science.nasa.gov/headlines/y2009/images/quadrupletransit/
quadtransit2009.gif>

"To photograph the smaller moons, you'll need a mid-sized backyard
telescope equipped with a good CCD camera," notes Go.

Hubble's observations are part of the Hubble Heritage Project, a 10-
year
outreach effort aimed at producing images of exceptional beauty for
the
general public. "Only 0.5% of Hubble's observing time is devoted to
Heritage work," says Noll, one of the project's leaders, "so we're
picky
about our targets." He thinks the quadruple transit could rank among
the
best planet-shots in Hubble's archive.

The images could yield hard science, too.

"The transit of Titan will be of particular interest," says Noll.
"Researchers plan to use Saturn as a backlight to probe the size and
transparency of the giant moon's atmosphere." Hubble will also capture
a
rare view of the rings almost edge-on, a point of view that can reveal
ring-warps, undiscovered satellites, and new information about the
reflectivity of ring particles.

"Hard science can be beautiful."

Stay tuned to Science{at}NASA for snapshots.

Editor's note: To find Saturn on Feb. 24th, look southwest before
sunrise. The planet is easy to see shining like a golden first-
magnitude
star in the constellation Leo: sky map
http://science.nasa.gov/headlines/y2009/images/greencomet/
skymap_north_lulin_24feb09.gif>.
By cosmic coincidence, Feb. 24th is also the date Comet Lulin
http://science.nasa.gov/headlines/y2009/04feb_greencomet.htm> makes
its
closest approach to Earth--and the comet is right beside Saturn! Using
a
small telescope you can catch a comet, a ringed planet and a quadruple
transit; it's a nice way to begin the day.
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