Iridium flare, atmospheric optical effects

Mark Hanning-Lee (
Thu, 02 Apr 1998 16:06:16 -0800

Sorry for cross-posting but this might interest readers of both groups.

Has anyone observed optical phenomena from a bright Iridium flare? I'm
including the corona (few degrees wide) that Jim Varney looked for,
caused by water clouds.

I'm also including 22 & 46 degree haloes, parhelia, circum-zenithal
arcs, and all the good effects that you can see around the sun or moon
in ice clouds.

Lastly how about an Iridium-bow? I've seen a moon-bow from a full moon.

I realize that all of these would be challenging; faint AND moving!
Ideal task for a CCD astronomer in brief exposures. Either set the
telescope stationary, or switch on the clock drive, or set the telescope
to follow clouds, e.g. slewing in a constant direction at a few
arc-minutes per second. (I'll explain why below).

Time wide-angle shots before / during / after an Iridium flare. Subtract
the during image from the average of the before/after images to remove
constant light sources & see if the result is significantly different
from 0! Any effect may be swamped by the effect of cloud motion, so that
the light-pollution glow on a patch of cloud changes on the same
timescale as Iridium flaring.

Best, Mark
Mark Hanning-Lee,