objects casting black shadows onto a light surface.
Simulations at three different magnifications. The objects could
be lunar soil grains, earthly rocks, sand or fir trees.
When looking direction away from the
sun (the centre of the simulations) shadows are hidden by the objects
themselves. Away from the antisolar point they become increasingly
The antisolar region is brighter because it contains less shadow and
more sunlit surfaces than its surroundings.
The lower simulations resemble the opposition effect as seen from
an aircraft over forests, deserts
and even cornfields.
The effect is sometimes visible from the ground - for example, it
can be seen on rough road
surfaces or in the dry powdery sand above the high water
line of a beach.
Antisolar brightenings have other causes. Retro-reflection might
also occur from isolated crystals within rocks and there is an effect
called coherent backscattereing. On Earth, where there
is nearly always plenty of water droplets around, the heiligenschein
produce their effects and these are sometimes hard to separate from
those made purely by shadow hiding.