I seek color in submitted witness reports, not necessarily to provide
additional scientific information (although it's data, so I wouldn't
completely rule out that possibility), but rather, to understand how
people see things differently, and to make for a more complete public
report, since public education about fireball events is part of our
function. Meteor color is as much a part of the phenomenon as
brightness, speed, fragmentation, and everything else. The fact that we
can't directly convert color into composition doesn't mean we shouldn't
include this information in a complete report.
Chris
*******************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
On 11/4/2015 4:48 PM, Matson, Rob D. via Meteorite-list wrote:
Hi John,
I think there are definitely things that can be learned by looking at the
spectroscopy
of fireball emissions, but of course such data are rare. And human
eyeballs/brains
are a poor substitute. We don't have the necessary spectral resolution, and of
course
the optical response is far from flat. It is perhaps not coincidental that
green-blue
(0.498 microns) is the peak of our scotopic response. Deep red (>0.63 microns)
sensitivity is almost non-existent in scotopic vision, so even if a fireball
had a
significant red component, a much smaller green component would swamp it just
due to our spectral response.
Since nothing really diagnostic can be learned from a witness's perception of a
fireball's color (as far as the meteoroid's composition is concerned), I see
little
point in asking them or encouraging them to report it. The next best thing
that a novice witness can report (other than an accurate time and duration)
is the slope of the meteor track relative to the horizon -- perhaps using a
clockface analogy to avoid scary geometry. If I know the approximate fall
zone reasonably accurately, a distant observer's slope approximation can
greatly narrow down the true flight bearing, even without azimuth information
(which can already be inferred from their location relative to the fall with
greater accuracy than they can report).
Mike Hankey has put together some very nice tools on the AMS site for
amateurs to contribute useful information, concentrating on those things
that non-technical people are reasonably good at. With enough witnesses,
the average solution can sometimes be fairly accurate, even if the individual
reports are all over the place. --Rob
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