From: Doug Jones (random@qnet.com)
Date: Tue Sep 19 2000 - 21:33:56 MDT
Amara Graps wrote:
>
> Here is another reference about it:
> http://www.weather-photography.com/Atmospheric_Optics/heiligenschein.html
>
> which says:
>
> "Heiligenschein is a bright spot of light around the shadow of the
> observer's head, cast on dewy grass land. The dew droplets on the
> grass act as lenses, focusing sunlight on the grass leaves, strongly
> illuminating them, and working again as a lens for the backscattered
> light. This effect is enhanced by the fact that in the antisolar
> point (the point opposite the sun, i.e. the shadow of one's head),
> no other shadows are present, and thus the region looks much
> brighter because the light and dark details of the surface are
> integrated by the eye. Look for the Heiligenschein early in the
> morning, when the sun is low and thus your shadow long, and move
> yourself to let the shadow be cast on wet dewy grass. The effect is
> very common, so you should be likely to see it."
Lunar regolith also shows a strong Heiligenschein due to the myriad tiny
glass spheres in it, produced by microimpacts. The Apollo lunar surface
journal has a .mov file of the Apollo 17 landing that shows this quite
well. See
http://www.hq.nasa.gov/office/pao/History/alsj/a17/video17.html
to download it.
-- Doug Jones, Rocket Plumber XCOR Aerospace
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