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FAQ: Gegenschein

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#1 Thick_asa_Planck

Thick_asa_Planck

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Posted 03 July 2005 - 12:18 PM

Gegenschein

What is it?

The "Gegenschein" (German for "counterglow") is a faint, elliptical (oval shaped) patch of light which appears in the region of sky that is opposite to the Sun, called the anti-solar region.

How is it formed?

The counterglow is formed via sunlight reflecting off billions of dust particles which lie in the ecliptic plane of the solar system.

Are Zodiacal Light and the Geigenschein the same thing?

They are not. They are created in similar ways, but the gegenschein has a much higher angle of reflection than the zodiacal light, which is visible nearer the horizon.

When can I see it?

The Geigenschein is most easily visible after midnight in early autumn or early spring months. At this time, the gegenschein resides in a region of sky with few stars, which means it will not be overshadowed by the light of the Milky Way.

How difficult is it to see?

The Gegenschein is regarded as perhaps one of the most elusive sky phenomenon from all but the darkest sites. Clear, dark, moonless skies are required to give the observer any chance of seeing this rare phenomenon. A high altitude observing location also helps quite a bit. Your eyes must also, as with zodiacal light, be well adjusted to the dark.

The Gegenschein has a low surface brightness, often less than zodiacal light, so using averted vision to see it works well here.

How difficult is it to photograph?

Because it is a faint target to say the least, long exposures (often upwards of 10 minutes) coupled with a high ISO speed must be taken in order to get the Gegenschein on film. A wide angle lens is also adviseable. There are many superb long exposure images around the internet of this photogenic target.

Related Links:

http://www.as.wvu.ed...h/skw9810h.html

Images of the Gegenschein:

http://antwrp.gsfc.n...d/ap990625.html

http://www.pbase.com.../image/33864124


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