Annular Solar Eclipse May 20, 2012
May 20, 2012 Annular Solar Eclipse (click the picture to bring up a full-size graphic). Link to full-size animated version (will appear in a new window)
On May 20th was a solar eclipse! Because of the Moon's elliptical orbit, the Moon was too far away from the Earth to totally cover up the Sun for those in the eclipse path. In such a case, the eclipse is called an "annular solar eclipse", because of the annulus (ring) of Sun that appears around the dark Moon when the Moon and Sun are exactly lined up. The chart below shows the path of the annular solar eclipse going through northern California and central Nevada on to New Mexico and western Texas. The chart also shows what the eclipse looked like from Redding and what we saw here in Bakersfield. Select the chart to download a PDF version suitable for printing.
In Redding the Moon covered up to 88% of the Sun's area. That's enough Sun to keep daylight conditions, though the sky looked a darker blue than usual. At maximum eclipse for us, the Moon covered up about 81% of the Sun's surface area. Your eyes adjusted enough to the dimming sunlight as the eclipse progressed that you probably didn't know an eclipse was going on if you didn't look toward the Sun (but just briefly!). After I give some more specifics for Bakersfield, I'll tell you how to safely observe an eclipse—very dark sunglasses do NOT protect your eyes!
On May 20th, we saw the Moon begin to cross the Sun at 5:22 PM when the Sun was about a third of the way up in the western sky. The maximum eclipse (81% Sun's surface area covered up) was at 6:36 PM. The Moon finished crossing the surface of the Sun at 7:41 PM (almost at sunset). You can get the stats for any other city in the U.S. by going to NASA's Javascript Solar Eclipse Explorer, selecting the city you want from the drop-down menu (or enter the latitude and longitude for smaller towns), and then clicking the particular century you want. Note that it does not know about daylight savings, so you have to subtract an hour from the "Time Zone" button before selecting the century button (e.g., for Bakerfield in May, the time zone will be "07:00 W" instead of "08:00 W").
Stats for Bakersfield May 20th eclipse from the Solar Eclipse Explorer:
| Eclipse begins | Sun altitude (degrees above horizon) | Maximum eclipse | Sun altitude | Sun azimuth (south=180º, west=270º) | Eclipse ends | Sun altitude | Eclipse magnitude (how much of Sun's diameter covered) | Eclipse obscuration (how much of Sun's surface area covered) |
|---|---|---|---|---|---|---|---|---|
5:22:20 |
30 |
6:36:28 |
15 |
285 |
7:41:37 |
2 |
87.2% |
81.2% |
The next solar eclipse for Bakersfield with at least this much of the Sun covered will be on August 22, 2044! There will be other partial solar eclipses with less covered up before then.
The Sun is extremely bright and you can damage your eyes within a few seconds if you look at the Sun without protection. To view the Sun during a partial or annular eclipse you need to either look at a projection of the Sun or use a special-purpose solar filter—very dark sunglasses do NOT protect your eyes. Other things to NOT use (they are NOT safe) include: smoked glass, stacked sunglasses, crossed polarizing shades, photographic neutral-density filters, or a filter designed to block visible light for infrared pictures. The items in the previous sentence do not block the UV or IR that can also damage your eyes. What follows are safe ways of viewing the Sun.
The simplest thing to use is a pinhole projection. Poke a hole in an index card with a thumb tack or sharp pencil, face the card toward the Sun and hold a second card three or four feet behind it in the front card's shadow. A big hole makes a bright but fuzzy image and a small hole made a dim but sharp image. You can reduce the daylight glare on the viewing card by enclosing the setup in a long box.
A sharper and bigger Sun image can be made by projecting the Sun's image through a small telescope or binoculars onto a white card behind the telescope or binoculars. Do NOT look through the telescope or binoculars without a special-purpose solar filter! You will need to have the telescope or binoculars on a mount. Point the telescope or binoculars toward the Sun using the device's shadow. When you are pointed at the Sun, the telescope's shadow will be smallest. At that time a bright image of the Sun will shine from the eyepiece onto the card. Turn your focus knob and adjust the distance of the card from the telescope until the Sun is sharp and as big as you want.
For direct viewing you can use an arc-welder's glass of shade #14 (NOT a lower-numbered shade) or special "eclipse glasses". High-quality and safe but inexpensive eclipse glasses are available from Thousand Oaks Optical and Rainbow Symphony, both U.S. manufacturers. The best views are through a properly-filtered telescope. The Kern Astronomical Society will probably have solar-filtered telescopes set out at a local viewing spot for you to look through—see the KAS website for the when and where. Other members are heading north to view the annular solar eclipse.
Solar filters for your telescope or binoculars can be found at Astro-Physics, Thousand Oaks Optical, and Orion Telescopes & Binoculars. The solar filters come as either wispy sheets of metallized film, metallized black polymer plastic, or metallized glass with the metallized film ones usually providing the very best view but all being very good. These filters fit over the front of the telescope or binoculars. Do NOT use small filters that fit over the eyepiece since the magnified and concentrated sun's energy can easily shatter an eyepiece filter (and then fry your eyeball). Below are some pictures I took with a solar filter of metallized film over a 300-mm telephoto lens with a 1.4X extender (so effective focal length 420 mm) from Bakersfield in late afternoon. Select the images to bring up a full-size image.
 Large sunspot group now almost all rotated away from us—look at 5 o'clock position at the edge. |
Below are other websites to check out for observing the Sun and more details about the May 20th eclipse.
Observing the Sun websites
- Sky and Telescope's How to Watch a Partial Solar Eclipse
- Mr Eclipse's Observing Solar Eclipses Safely
- TransitOfVenus.Org's Safe Viewing Techniques
- Doug Duncan's How to Safely Watch the Sun
- Ralph Chou's Eye Safety During Solar Eclipses and Eclipse Filters
- Rainbow Symphony's Eclipse Glasses
May 20th Annular Solar Eclipse
- NASA's May 20th Annular Solar Eclipse site (Observer's Handbook)
- NASA Javascript Solar Eclipse Explorer: quickly calculate the local circumstances of an eclipse from any geographic location. Extended version for U.S. cities.
- Google map of May 20th eclipse
- Sky and Telescope's Resources for the May 20th Eclipse
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last updated: May 22, 2012
Webpage contact: Nick Strobel
