Bakersfield Night Sky – May 5, 2012
By Nick Strobel
Two weekends from now on May 20th will be a solar eclipse! Because of the Moon's elliptical orbit, the Moon will be 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 first 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 will look like from Redding and what we'll see here in Bakersfield. In Redding the Moon will cover up to 88% of the Sun's area. That's enough Sun to keep daylight conditions, though the sky will look a darker blue than usual. At maximum eclipse for us, the Moon will cover up about 81% of the Sun's surface area. Your eyes will adjust enough to the dimming sunlight as the eclipse progresses that you probably wouldn'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 the eclipse—very dark sunglasses do NOT protect your eyes!
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).
Whatever you use for observing the May 20th eclipse, save it for the Venus Transit that happens on June 5th. On that date Venus will cross in front of the Sun (from 3:05 PM to 9:45 PM in Bakersfield). This will be the last time for another 105 years for such an event. We will have to wait until 2117 for another Venus transit.
In tonight's sky Venus is still quite high and brilliant in the western sky—see the second chart below. It will set at about 10:30 PM. Venus is starting its plunge back toward the Sun and its fall over the following few weeks will be dramatic. Jupiter is now gone from our sky and will pass behind the Sun on May 13th. Mars is already high in the southern sky at sunset next to the stars of Leo. Saturn is already about a third of the way up in the southeastern sky to left of Spica of Virgo by the time the Full Moon rises—see the third chart below. This will be the largest full Moon of 2012—the Moon will be near its closest point in its elliptical orbit for this full phase. Two weeks later, it will be near its farthest distance from the Earth at new phase to make the annular solar eclipse.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com