الثلاثاء، 31 مارس 2015

Protect your eyes while watching solar eclipses




The Sun’s UV radiation can burn the retinas in the eyes leading to permanent damage or even blindness. This can occur even if your eyes are exposed to direct sunlight for just a few seconds. How to view a solar eclipse The only way to view the uneclipsed or partially eclipsed Sun safely is to project or filter the Sun's rays. Some safe options: Pinhole projector: An easy and cheap way to view the Sun is to project its image to a screen, such as a sheet of white paper or cardboard. Projection works well with or without a telescope or binoculars. However, don't look through the telescope’s eyepiece or side-mounted finder scope while projecting the Sun's image to a screen. How to make a pinhole projector Eclipse glasses: If you are not the D.I.Y. type, check in with your local natural history or space museum or your local astronomy club for where to rent or buy eclipse glasses. Welder's goggles: NASA recommends welder's glasses rated 14 or higher. These can be found at your local welding supply store. Keep in mind that welder glass grading may be different in different countries. Aluminized Mylar sheeting: Mylar can be easily cut with scissors but make sure that the sheets you use are aluminized and that you take the advice of experts while using it. You can use special solar filters to see the Sun during a solar eclipse, but use the proper type of solar filter that is designed for eclipses. Check that filters do not crack under the Sun’s magnified and focused intensity. Solar filters must be treated with care or they can quickly become damaged and unsafe to use. How to take sunrise and sunset pictures How not to view a solar eclipse It goes without saying that you should never look directly at the Sun without any protective eyewear before, after or during a solar eclipse. According to NASA, the following materials should never be used to view a solar eclipse: Color film. Medical X-ray film with images on them. Smoked glass. Any kind of sunglasses. CDs or floppy disks. The bottomline is, do not take any chances. If you are unsure about the safety of a viewing device, talk to an expert first before using it.




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