StarWatch for the greater Lehigh Valley
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JUNE  2017

JUNE STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

Print Large Sky Charts For 10 p.m. EDT:   NORTH | EAST | SOUTH | WEST | ZENITH

[Moon Phases]
 
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Status Current Moon Phase
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1085    JUNE 4, 2017:   Eclipse Viewing on the Cheap
Preparation for the total solar eclipse that sweeps across our country on Monday, August 21 should be occurring now. In fact, if you are interested in obtaining lodging along the path of totality, where the moon completely covers the sun, accommodations were already difficult to obtain during the summer of 2016. However, enthusiasts all across the continental US will be treated to a partial solar eclipse, where part of the sun will be covered by the moon. Anytime a partial solar eclipse is occurring, or for that matter anytime the sun is visible, presents a dangerous situation for retinal damage if the sun is observed directly without any appropriate filtration. It seems that everyone knows this, but during eclipse mania, the public wants to sneak a peek. The glance may turn into a stare, and that is where significant eye damage can occur. In addition, the extreme brightness of the sun will foil any unfiltered attempts to see the dark moon covering Sol. For younger children, I suggest a projection system which is easy to construct and to use. Obtain a long box, maybe in the range of two to three feet. On one of the long ends of the box, cut a hole several inches in diameter and tape to its surface a piece of aluminum foil perforated with a small pinhole. The optimum ratio of pinhole size to box length is 1 to 400. On the other end, glue or tape several thicknesses of white paper to the back of the box, or paint it white to act as a screen. Then cut a rectangular opening, perhaps three inches long by one inch wide near the screen of the box as a peephole to allow the screen to be visible. The child takes the box and puts it on his shoulder with his back towards the sun, the pinhole aperture facing Sol. On a clear day, the pinhole will project a safe image of the partially eclipsed sun onto the screen. Here are other ways of creating pinhole images of the sun which are even easier. Take a colander and a white bed sheet. Hold the colander in the direction of the sun, and allow its holes to project images of the partially eclipsed sun onto the bedding, or let the motions of leaves on a tree project thousands of solar images onto a white sheet which is placed beneath it. Even the holes in a Ritz cracker will work, if you don’t eat the snack. These are simple, inexpensive, and extremely safe methods to view a partial solar eclipse. Pictures are online at astronomy.org/StarWatch/June/index-6-17.html#6-4-17.

[Solar Projection Box]
Construct a Solar Projection Box: From Bryan Brewer, Eclipse, Earth View, 1979, p. 82...

[Solar Projection]
Crisscrossed fingers easily project the sun. The dark disk in the inset photo is a penny. Gary A. Becker images...

[Solar Projection]
Tree leaves, a colander and even Ritz crackers will project the sun's image of the partial eclipse. Watch how the temperature drops as the moon obscures the sun during the partial phases. Gary A. Becker large and inset eclipse images/collander and thermometer, Internet...
 

1086    JUNE 11, 2017:   Filtered Solar Eclipse Viewing
Last week, I wrote about safe and inexpensive solar projection techniques for viewing the August 21 total solar eclipse. If you are not positioned along the narrow path of totality that stretches across the continental US from Oregon to South Carolina, then all aspects of the eclipse will be partial, and at no time will it be safe to view the sun unless the image of Sol is safely projected or filtered. The eye acts like a lens, focusing light onto the fovea and retinal net. “The mechanism by which retinal tissue damage occurs in solar retinopathy (retinal ‘disorder’ burn) is photomechanical [and chemical] in nature (Ross Bronson Chod, MD),” due to the sun’s brightness. This situation may be thermally enhanced if the retina is heated by infrared radiation from the sun, but it should be noted that staring into any bright light source is bad for the eyes. In addition the retinal net has no pain sensors, making it difficult at the time of observation to realize that any damage is occurring. In most cases, patients with solar retinopathy make partial to full recoveries after about 18 months, but you’d be plain stupid to take any chances. In addition, the overwhelming brightness of the sun hides the moon in a total solar eclipse until about 15 seconds before totality. Filtering the sun’s light is an inexpensive alternative that produces a much sharper image than the simple projection techniques discussed last week, but the solar intensity must be reduced by about 99.99 percent before safe solar viewing can occur. Here are some suggestions. Go to any welding supply store and purchase a No.14 welder’s filter. They come in two different varieties. A less expensive version produces a green representation of the sun, and for a few dollars more, a filter that is “gold” coated which will give the observer a more natural view of Sol. You can also buy goggles, usually red in color, with a filter holder in front and watch the eclipse in a chaise lounge while relaxing and sipping a margarita. My recommendation, however, is to purchase a pair of black, Mylar eclipse glasses which can be worn just so or over regular glasses. None of these filtering techniques are meant to be used at the eyepiece end of a telescope or binoculars. The focused light from the sun will melt the Mylar or crack the welder’s filter. Contact Rainbow Symphony for your Mylar eclipse glasses at https://www.rainbowsymphony.com/eclipse-glasses/ or stop into the Collier Hall of Science office at Moravian College where Lou Ann Vlahovic (610-861-1425) will sell you as many as you would like for just a buck each. Do it now before the big rush in a few weeks.

[Solar Filtration]
Safe solar Filtration which will create a sharp distinct view of the eclipsed sun can be accomplished very inexpensively. Left, Joe Hall wears eclipse glasses which produce a natural yellow image of the sun while recent Moravian graduate, Tracy A. Laurie-Lakhram, demonstrates the use of welder’s goggles with a No. 14 gold filter attached in front. Never use these filters on the eyepiece end of telescopes or binoculars. Gary A. Becker photography from the Sky Deck of the Collier Hall of Science...
 

1087    JUNE 18, 2017:   
 

1088    JUNE 25, 2017:   
 

[June Star Map]

[June Moon Phase Calendar]
 

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