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Stockton Astronomical Society Eclipse Page

On May 20th, 2012, a partial annular eclipse will occur in and around Stockton, California. Stockton and surrounding towns are not on the centerline of this eclipse, but it will be the deepest eclipse Stockton has encountered in decades, and this page will address the details of this upcoming event.

First of all, you will damage your eyes permanently if you attempt to view the eclipse without appropriate protection.

What is an annular eclipse? Does this happen once a year? How is it different from a total solar eclipse or a lunar eclipse? Here is a brief description of eclipses including an annular eclipse.

Total Lunar Eclipse

Moon during a total Lunar Eclipse. Photo by SAS member Ray Lukaszewski.

 

There are Solar Eclipses and there are Lunar Eclipses. A lunar eclipse is when the Earth passes between the Sun and the Moon and the Earth's shadow is cast upon the Moon causing it to appear dark.


Total Solar Eclipse

Total Solar Eclipse showing the Sun's corona only viewable when the glare of the Sun is removed by the Moon. Photo by SAS member Carlos Avalle.

Solar eclipses occur when the Moon passes in front of the Sun as viewed from locations on the Earth.

During a total solar eclipse, the shadow of the Moon is usually quite small on the Earth, and only within the shadow do you see a total eclipse. All other places witness either a partial eclipse or no eclipse at all.

The Moon orbits the Earth not in a circle but more of an elliptical orbit, therefore the distance to the Moon varies. When it is closer, it looks a bit bigger, and when it is further it looks a bit smaller. The Earth orbits the Sun in an ellipse, so we are sometimes a bit closer and sometimes a bit further, so the Sun also appears larger and smaller by a small amount. The sun is basically 400 times further than the Moon, but is also 400 times larger, so they appear nearly the same size in the sky.


Annular Eclipse

Annular Eclipse [using a full-aperture safe solar filter]. Photo by Grant W. McKinney.

When the Sun is a bit further and looks a bit smaller, and the Moon is a bit closer and looks a bit bigger, then when the Moon moves in front of the Sun it totally covers the Sun, and the eclipse is total. However, when the Sun looks a bit bigger and the Moon looks a bit smaller, then when the Moon moves in front of the Sun it looks smaller than the Sun and cannot block it completely.

So when this type of eclipse occurs, you can see [using proper filtration] the Sun surrounding the Moon like a big hula hoop. This shape is called an annulus, and so we call it an annular eclipse. So the word "annular" does not refer to "once a year" but actually the "annulus" or ring shape of the sun surrounding the moon resulting in the illusion of the eclipse.

 


The path of this upcoming annular eclipse starts near Hong Kong, moves across the Pacific Ocean, and comes down toward the United States. It enters the USA near Crescent City, passes over Mt. Lassen, through Reno, and heads toward the southeast. For an interactive map showing the path of the eclipse, visit http://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2012May20Agoogle.html. If you are within a few dozen miles of this path you will be able to see the Sun surrounding the Moon for a few moments, an annular eclipse.

Stockton is quite a bit south of this center-line, so the Moon will not appear to be within the Sun's disk, and the annular eclipse will not be complete. However, the Sun will be blocked by a large amount, the most for viewers in Stockton in decades. This is called a partial solar eclipse.

The brightness of the sky will fall quite a bit, but since your eyes adjust themselves automatically, you may or may not notice that anything at all is occurring. It may even cool off a bit since the intensity of the Sun's energy will be blocked by the Moon. It will not become dark like a total solar eclipse.

Even though the Sun is mostly blocked by the Moon, it is still extremely dangerous to look at this event. The surface of the Sun will still be as bright as any other day, and that intensity will destroy your eyes. Please do NOT look at this eclipse without proper filtration.

 

For Stockton, the eclipse will be occurring from 5:20 PM to 7:39 PM with the maximum eclipse occurring at 6:30 PM. The Sun will be low in the west-northwest setting at 8:13 PM. At maximum eclipse the sun will be 18° high.

There are a few ways people damage their eyes when looking at eclipses.

  1. Photographic film is NOT a safe way to observe an eclipse.
  2. Never look directly at the Sun with your eyes nor with an unfiltered telescope.
  3. Do not use eyepiece filters to observe the Sun with your telescope.
  4. Never use binoculars to view the Sun, even during an eclipse.
  5. Hole burned through a lens cap.

    Photo by SAS member Ray Lukaszewski.

    When pointing a telescope toward the Sun, the finderscope is also pointing toward the Sun. If the main scope has a filter and the finderscope doesn't, the finderscope is just as dangerous as the main scope. Here is a photograph of a hole burned into the eyepieces cap by the Sun shining through the finderscope. The same thing would happen to your eyeball.

There are a few good ways to safely view this event. Clicking on each method will take you to a "how-to" site.

  1. Pinhole Viewers.  http://www.exploratorium.edu/eclipse/how.html#PIN2
  2. Projection.  http://www.spaceweather.com/sunspots/doityourself.html
  3. http://www.3rf.org/wp-content/uploads/2010/03/Projecting-an-Image-of-the-Sun-2-lessons.pdf
  4. Leaves of trees.  http://apod.nasa.gov/apod/ap100123.html
  5. Telescopes with full-aperture filters.  http://www.eaas.co.uk/news/solar_observing.html
  6. Reflect the Sun's image onto a distant wall with a very small mirror.
  7. TV
  8. Attend the Stockton Astronomical Society's eclipse event along the waterfront at the west side of Weber Point where we will have safe viewing systems for the public.

 

There are some myths and superstitions out there regarding eclipses. One is that if you are pregnant then you must wear a copper belt to protect your fetus. This is nonsense. One is that the alignment of the Sun-Moon-Earth will cause gravitational constructive forces and that earthquakes and volcanic eruptions will occur at a higher frequency. This is nonsense. There are others. If you have any questions regarding which are true and which are not, please call the Stockton Astronomical Society and we will guide you to a rational and logical conclusion.

Again, there is never enough caution to exercise when attempting to view the Sun, even when eclipsed. The destruction to your eye is immediate, intense, irreparable, and inexcusable. Never look at the Sun. The heat energy will ruin your eyes. Without a telescope it may be tempting to stare at the Sun. You will feel no pain and you will think that because it doesn't hurt that nothing is wrong. Unfortunately, your eyesight will be ruined, and it can't be fixed. If you are using a telescope and you look at the Sun, the heat energy will immediately explode your eye. It will rupture, literally burn, and will literally ruin your life.



Copyright © 2011 - 2012 by Stockton Astronomical Society
Last Updated: 5/2/2012
http://www.stocktonastro.org/EclipsePage.html