Steele Hill
STEREO and SOHO Project

March 1, 2007

Two Eclipses, One Observed Only by NASA

That's right! The Moon is the central figure in two different kinds of
eclipses within one week. Here's how. A total lunar eclipse, partly visible
from every continent around the world, will occur on March 3 when the Moon
will pass into and out of the shadow of Earth. The Moon will appear to glow
with a distinct reddish cast. The entire event will be visible from Europe,
Africa and western Asia. In eastern Asia, Moonset occurs during various
stages of the eclipse. For example, the Moon sets while in total eclipse
from central China and southeast Asia. Western Australia catches part of the
initial partial phases but the Moon sets before totality. Observers in
eastern North and South America will find the Moon already partially or
totality eclipsed at Moonrise. From western North America, only the final
phases are visible.

Here in the United States, you have to be in the eastern half of the country
to see the total eclipse. At the end of the day on Saturday, go outside and
face east. As the sun sets in the western skies, a red Moon will rise before
your eyes -- fantastic! Maximum eclipse is at 6:21 p.m. EST. The next total
lunar eclipse will occur on August 28 this summer.

On Feb. 25, 2007 there was another kind of eclipse of the Moon when it
crossed the face of the Sun -- but it could not be seen from Earth. This
sight was visible only from the STEREO-B spacecraft in its orbit about the
sun, trailing behind the Earth. NASA's STEREO mission consists of two
spacecraft launched in October, 2006 to study solar storms. The transit
started at 1:56 am EST and continued for 12 hours until 1:57 pm EST.
STEREO-B is currently about one million miles from the Earth, 4.4 times
farther away from the Moon than we are on Earth. As a result, the Moon will
appear 4.4 times smaller than what we are used to. This is still, however,
much larger than, say, the planet Venus appeared when in transited the Sun
as seen from Earth in 2004. This alignment of STEREO-B and the Moon was not
just due to luck. It was arranged with a small tweak to STEREO-B's orbit
last December. The transit is quite useful to STEREO scientists for
measuring the focus and the amount of scattered light in the STEREO imagers
and for determining the pointing of the STEREO coronagraphs. The Sun as it
appears in these the images and each frame of the movie is a composite of
nearly simultaneous images in four different wavelengths of extreme
ultraviolet light that were separated into color channels and then
recombined with some level of transparency for each.

[NOTE: Images and weblinks supporting this article are available at
http://www.nasa.gov/mission_pages/st...Eclipse07.html ]