Top Document: [sci.astro] General (Astronomy Frequently Asked Questions) (2/9) Previous Document: B.11 Why does the Moon look so big when it's near the horizion? Next Document: B.13 Can stars be seen in the daytime from the bottom of a tall chimney, a deep well, or deep mine shaft? See reader questions & answers on this topic! - Help others by sharing your knowledge Author: Joseph Lazio <jlazio@patriot.net>, Steve Willner <swillner@cfa.harvard.edu> This question appears most frequently near the time of solar eclipses. The short answer is no! The unobscured surface of the sun is as bright as ever during a partial eclipse and just as capable of causing injury. The injured area on the retina may be a bit smaller, of course, but that's no reason to risk damage. Moreover, there are no nerve endings in the retina, so one can do permanent damage without being aware of it. People have proposed a host of methods for viewing the Sun, including exposed film and CDs. These home-grown methods typically suffer from two flaws. First, they do not cut out enough visible light. Second, they provide little protection against ultraviolet or infrared light. The only safe method for viewing the Sun directly is using No. 14 arc-welder filter or a metallicized glass or Mylar filter. A local hardware store or construction supply store should carry or know where to obtain arc-welder filters. Many astronomy magazines carry ads for solar filters. Whatever filter you use, inspect it to make sure it has not been damaged. Even a pinhole can let through enough light to cause injury. If you use a filter over a telescope or binocular, make sure the filter is firmly attached and cannot come off accidentally! Never use an eyepiece filter, which can overheat and crack. Any filter should cover the entire entrance aperture (or more precisely, any part of the entrance aperture that isn't covered by something completely opaque). If using only one side of a binocular, cover the other side. An alternative way to view the sun is in projection. You can use a pinhole camera or a telescope, eyepiece, and screen. Many observing handbooks illustrate suitable arrangements. This method is not only safe, it can give a magnified image and make it easier to see details. If you are lucky enough (or put in the advance planning) to see a total solar eclipse, the total phase can be enjoyed with no eye protection whatsoever. In fact, experienced eclipse-goers often cover one eye with a patch for several minutes before totality so the eye will be dark-adapted during totality. Just be sure to look away (or through your filter again) the instant totality is over. Additional information on the safe viewing of solar eclipses is at the Eclipse Home Page, <URL:http://sunearth.gsfc.nasa.gov/eclipse/>. User Contributions:Top Document: [sci.astro] General (Astronomy Frequently Asked Questions) (2/9) Previous Document: B.11 Why does the Moon look so big when it's near the horizion? Next Document: B.13 Can stars be seen in the daytime from the bottom of a tall chimney, a deep well, or deep mine shaft? Part0 - Part1 - Part2 - Part3 - Part4 - Part5 - Part6 - Part7 - Part8 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jlazio@patriot.net
Last Update March 27 2014 @ 02:11 PM
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