Solar eclipse

:Solar Eclipse is also an alien friend of the rubber doll Betty Spaghetty.

Observing a solar eclipse

Looking at the Sun is dangerous at any time when any part of the brilliant visible disk of the Sun (its photosphere) is visible; to do so can cause permanent eye damage. This is true at any time, including during solar eclipses; since an eclipse offers an unusually high temptation to look at the Sun, there is a high incidence of eye damage caused during solar eclipses. Viewing the Sun through any kind of optical aid ?binoculars, a telescope, or even a camera's viewfinder? is extremely dangerous.

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Safe Solar Viewing

• NEVER look directly at the sun with binoculars or telescope etc - NEVER even look at the sun with the naked eye - Eye damage will result, which may cause permanent blindness!

The Sun can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Note that sunglasses are of little use, since they don't block the harmful and invisible infra-red radiation which causes retinal damage; other improvised methods, such as using a reflection in water, or looking through a compact disk, are equally dangerous. Only properly designed and certified solar filters should ever be used for direct viewing of the Sun; and these must be in perfect condition, as even a small defect could cause damage.

Related Topics:
Infra-red - Compact disk

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The safest way to view the Sun is by indirect projection. This can be done by projecting an image of the sun onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera. The projected image of the sun can then be safely viewed; this technique can be used to observe sunspots, as well as eclipses. However, care must be taken to ensure that no-one looks through the projector (telescope, pinhole, etc.) directly, as this will cause severe eye damage; particular care should be taken if children are present.

Related Topics:
Pinhole camera - Sunspot

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It is safe to directly observe the total phase of a total solar eclipse, when the Sun's photosphere is completely covered by the Moon; indeed, this is a very beautiful sight. The Sun's faint corona will be visible, and even the chromosphere, solar prominences, and possibly even a solar flare may be visible. The danger here is of being caught out by the end of the total phase, and the return of the "exposed" Sun; because all parts of the Sun's disk are of similar intensity, even a tiny sliver of the Sun could cause permanent eye damage. For this reason, viewing the total phase of a solar eclipse through binoculars or a telescope should not be recommended.

Related Topics:
Corona - Chromosphere - Solar prominence - Solar flare

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For more information on safe eclipse viewing, see:

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• Eye Safety During Solar Eclipses, Fred Espenak, NASA Goddard Space Flight Center
• How to Watch a Partial Solar Eclipse Safely, Alan M. MacRobert, Sky & Telescope magazine