Information about the May 20, 2012 Annular Solar Eclipse
http://www.mreclipse.com/MrEclipse.html
Fred Espenak (aka Mr. Eclipse) produces the eclipse info for NASA. This website has plenty of info from safe
viewing techniques to tips on photographing solar and lunar events.
Starts in the Far East at dawn, tracks eastward across the north Pacific and ends at sunset in western Texas.
Redding, CA lies 30 kilometers
south of the central line.
Nevertheless, it still experiences an
annular phase lasting 4 1/2 minutes
beginning at 01:26 UT. It is already
late afternoon along this section of
the eclipse path. The Sun's altitude
is 20° during the annular phase and
decreasing as the track heads
southeast. Central Nevada, southern
Utah, and northern Arizona are all
within the 185 mile wide “Path of
Annularity”
http://eclipse.gsfc.nasa.gov/OH/OH2012.html LOTS of info about this eclipse, click on Table 3 to see the local
circumstances for numerous U.S. cities, remember that times are in Universal Time (Greenwich Time, -7 for PDT).
Or go directly to the list of US cities: http://eclipse.gsfc.nasa.gov/OH/OHtables/OH2012-Tab03.pdf
Here are a few California example (I’ve converted to local times):
City
start time
mid eclipse
end time
Eureka
San Francisco
San Diego
5:10pm
5:16
5:28
6:28pm
6:33
6:40
7:37pm
7:40
7:43 (at sunset)
Magnitude
94%
90%
83%
Annular Duration
3 minutes 59 seconds
very deep partial
partial
Magnitude means how much of Sun’s diameter covered by Moon, a bit different from how much of the Sun’s disc (surface) is covered.
http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2012May20Agoogle.html
This gives you an interactive Google map where you can put the marker on any location and you’ll see the times (in Universal
Time, subtract 7 hours for PDT). For example, near Shasta, close to the center line, the local times are as follows:
Start of Partial Eclipse 5:17 pm, Start of Annular Eclipse 6:26, Max Eclipse 6:28, End of Annular 6:30, End of Partial 7:36.
So the entire event lasts 2 hours and 19 minutes, and the “Ring of Fire” Annular portion lasts over 4 minutes.
A Total eclipse in the umbra
B Annular eclipse in the antumbra.
C Partial eclipse in the penumbra
Annular Solar Eclipses (from http://www.mreclipse.com/Special/SEprimer.html )
Unfortunately, not every eclipse of the Sun is a total eclipse. Sometimes, the Moon is too small to cover the
entire Sun's disk. To understand why, we need to talk about the Moon's orbit around Earth. That orbit is not perfectly
round but is oval or elliptical in shape. As the Moon orbits our planet, it's distance varies from about 221,000 to 252,000
miles. This 13% variation in the Moon's distance makes the Moon's apparent size in our sky vary by the same amount.
When the Moon is on the near side of its orbit, the Moon appears larger than the Sun. If an eclipse occurs at that time, it
will be a total eclipse. However, if an eclipse occurs while the Moon is on the far side of its orbit, the Moon appears
smaller than the Sun and can't completely cover it. Looking down from space, we would see that the Moon's umbral
shadow is not long enough to reach Earth. Instead, the antumbra shadow reaches Earth.
The track of the antumbra is called the path of annularity. If you are within this path, you will see an eclipse
where a ring or annulus of bright sunlight surrounds the Moon at the maximum phase. Annular eclipses are also
dangerous to look directly with the naked eye. You must use the same precautions needed for safely viewing a partial
eclipse of the Sun (see: Observing Solar Eclipses Safely).
Annularity can last as long as a dozen minutes, but is more typically about half that length. Since the annular
phase is so bright, the Sun's gorgeous corona remains hidden from view. But annular eclipses are still quite interesting to
watch. You can read reports about the annular eclipses of 1999 in Australia and 2003 in Iceland. More recently, visit the
2005 Annular Solar Eclipse Photo Gallery.
This is what a partial eclipse looks
like. This image shows approximately 50% eclipse.
It’s not that 50% of the sun is covered, rather that the
Moon has progressed across 50% of the Sun’s
diameter.
This is what an Annular Eclipse looks like when you
are in that narrow path of “annularity”
SAFE VIEWING – there are a variety of ways to observe a partial or Annular Eclipse safely. Of course, you
should NEVER LOOK DIRECTLY AT THE SUN, even if it is not painful certain wavelengths can seriously
damage your eyes. (In a TOTAL solar Eclipse, filters are safely removed during totality in order to see the corona,
which is not visible during an Annular eclipse). You can project the image of the crescent sun through anything
with a small (± pencil size) hole (ideas are described in some of the websites listed). Or you can see the Sun
directly through SAFE SOLAR FILTERS. Eclipse Shades (eclipse glasses) are one type of safe filter.
If you really want some magnification, you can put the filter on the FRONT of a pair of binoculars, but you
MUST fix/tape the filter on so that there is NO possibility of unfiltered light passing through and causing instant
damage to your precious eyeballs. (I include this information to make sure you don’t put the shades/filter between
the optics and your eye, the intensity of magnified light and heat can melt the filter and then damage your eyes.)
______Please be extra-careful when guiding children in observing this amazing natural spectacle!_________
And save your Eclipse Shades for the JUNE 5TH
Transit of Venus
This is a very rare event (next time is in
2117), when the planet Venus passes in front of the
Sun and a small black spot can be seen crossing the
upper half of the Sun. Starts at 3:03pm PDT, and is
still in progress (in the “Lower 48”) as the sun sets.
Fascinating history… did you know that
observing the 1769 Transit of Venus was the primary
reason for Capt. Cook’s first voyage to the So. Pacific?
Do an internet search for “Transit of Venus” and find
a wealth of viewing tips and historical facts!
http://eclipse.gsfc.nasa.gov/transit/venus0412.html