Posted on 03/26/2015 7:06:18 PM PDT by Star Traveler
Nova Scotia will be fine in 2017 for 364 days...just don’t go there on August 21.
If you happened to fall asleep for about three minutes, you probably would have missed it ... LOL ... and that would be three minutes, only, in the last 38 years ... :-) ...
//////////////////////////////////////////////////////////
The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse. Partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions. Even when 99% of the Sun's surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection [Chou, 1981; Marsh, 1982]. Do not attempt to observe the partial or annular phases of any eclipse with the naked eye. Failure to use appropriate filtration may result in permanent eye damage or blindness!
Generally, the same equipment, techniques and precautions used to observe the Sun outside of eclipse are required for annular eclipses and the partial phases of total eclipses [Reynolds & Sweetsir, 1995; Pasachoff & Covington, 1993; Pasachoff & Menzel, 1992; Sherrod, 1981]. The safest and most inexpensive of these methods is by projection, in which a pinhole or small opening is used to cast the image of the Sun on a screen placed a half-meter or more beyond the opening. Projected images of the Sun may even be seen on the ground in the small openings created by interlacing fingers, or in the dappled sunlight beneath a leafy tree. Binoculars can also be used to project a magnified image of the Sun on a white card, but you must avoid the temptation of using these instruments for direct viewing.
The Sun can be viewed directly only when using filters specifically designed for this purpose. Such filters usually have a thin layer of aluminum, chromium or silver deposited on their surfaces that attenuates ultraviolet, visible, and infrared energy. One of the most widely available filters for safe solar viewing is a number 14 welder's glass, available through welding supply outlets. More recently, aluminized mylar has become a popular, inexpensive alternative. Mylar can easily be cut with scissors and adapted to any kind of box or viewing device. A number of sources for solar filters are listed below. No filter is safe to use with any optical device (i.e. - telescope, binoculars, etc.) unless it has been specifically designed for that purpose. Experienced amateur and professional astronomers may also use one or two layers of completely exposed and fully developed black-and-white film, provided the film contains a silver emulsion. Since all developed color films lack silver, they are always unsafe for use in solar viewing.
Unsafe filters include color film, some non-silver black and white film, medical x-ray films with images on them, smoked glass, photographic neutral density filters and polarizing filters. Solar filters designed to thread into eyepieces which are often sold with inexpensive telescopes are also dangerous. They should not be used for viewing the Sun at any time since they often crack from overheating. Do not experiment with other filters unless you are certain that they are safe. Damage to the eyes comes predominantly from invisible infrared wavelengths. The fact that the Sun appears dark in a filter or that you feel no discomfort does not guarantee that your eyes are safe. Avoid all unnecessary risks. Your local planetarium or amateur astronomy club is a good source for additional information.
In spite of these precautions, the total phase of an eclipse can and should be viewed without any filters whatsoever. The naked eye view of totality is completely safe and is overwhelmingly awe-inspiring!
Chou, B. R., "Safe Solar Filters," Sky and Telescope, August 1981, p. 119.
Marsh, J. C. D., "Observing the Sun in Safety," J. Brit. Ast. Assoc., 1982, 92, 6.
Pasachoff, J. M., and Covington, M., Cambridge Guide to Eclipse Photography, Cambridge University Press, Cambridge and New York, 1993.
Pasachoff, J. M. Field Guide to the Stars and Planets, 4th edition, Houghton Mifflin, Boston, 2000.
Golub, L. and Pasachoff, J. M. Nearest Star: The Exciting Science of Our Sun, Harvard University Press, 2001.
Reynolds, M. D. and Sweetsir, R. A., Observe Eclipses, Astronomical League, Washington, DC, 1995.
Sherrod, P. C., A Complete Manual of Amateur Astronomy, Prentice-Hall, 1981.
///////////////////LibWhacker sez/////////////////////
Remember: #14 Welder's Glass is safe PROVIDED there are no manufacturing defects in the glass or other damage caused by rough or improper handling, damage that you may not be able to see with your naked eye.
The real question is, how can you tell if a glass is damaged or defective? Are you willing to bet your eyesight on it? Unless you have lots of sophisticated equipment with you, you probably can't.
But by all means, do buy some #14 glass from a reputable source. It's not expensive. I've used it many times looking for large sunspots and viewing partial eclipses, without ill effect.
Still, whatever you do, DO NOT plant yourself on your back in the grass and stare up at the Sun for an hour or two at a time, say, thinking you'll be safe just because you're using a #14 welder's glass.
To protect your eyesight, you have to be a little more circumspect than that, viewing only a few seconds at a time, in full awareness that damage is cumulative.
Be a little skeptical about advertised features, as I'm sure you already are when reading or listening to ads.
As the article says, the safest way to view the sun, whether during an eclipse or not, is by projecting its image on a flat surface and only looking that (don't look directly through the projecting lens!).
Also interesting: In order to fully appreciate an eclipse you must, at some point, put down the glass and look at the sun with your naked eye, au naturel, BUT ONLY DURING THE MINUTE OR TWO OF TOTALITY.
Therefore, you MUST know when totality begins and ends for your location. It'd be nice if you could tag along with an astronomy club that has an astronomer on site to keep track of such things, who will tell you when to start naked eye viewing and when to stop.
Your so vain
I plan to be off the coast of S.C. in my sail boat under the path.
If not, in the car driving I-26 looking for clear.
bookmark
I’m hoping Kentucky will be my fourth. Saw 1979, Curacao in 1998? & France in 1999... Traveled to the 2nd and 3rd. The one in 1979 I was in elementary school.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.