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Re: (meteorobs) Re: Meteor colors

Ulrich wrote:

>>The main result of the work was, that the brighter the meteor is, the more
>>it is  coloured blueish or greenish and vice versa the fainter it is the
>>more redish it is.

        I've been reading your messages with interest.  Could your comment
above be the result of your CCD being more sensitive at the red end of the
spectrum thus recording faint meteors as red?  I'm a meteor spectroscopist
and have studied the intensity of spectral lines in meteors.  Fast meteors
tend to have strong Ca+ (h & K) lines at the blue violet end of the
spectrum.  Na1 and Mg1 is stronger in slower meteors.  Meteors tend to have
strong radiation at the blue end of the spectrum where CCD cameras have low
sensitivity unless they are back lit.  The color of meteors have a
correlation with the energy levels or temperature so fast meteors tend to be
white.  Back in the late 1960's and early 1970's Gale A. Harvey, NASA/LRC,
used photoelectrically activated shutters on high speed Maksutov Meteor
cameras to prevent stray lights from setting off his shutters. He blocked
much of the light except for the blue where meteors tend to have strong
emmission.  This worked with one exception, lightning on the horizon would
set off his shutters.  In DWR McKinleys book, Meteor Science and
Engineering, he made a note of Millman's and Hoffeit's work in 1937 were
they stated that the color index of bright meteors is ~-1.8  on blue
sensitive plates.  Jacchia's study in 1957 noted that the color index for
faint meteors was ~-1, possibly because the peak sensitivity of the eye
moves toward the blue for faint light sources, (Purkinji effect).  You
indicate the opposit so I suspect the red sensitivity of your CCD's may have
something to do with this.  It's something to investigate.  There is a paper
on the color index of meteors in the Astronomical Journal 62 p.358-362 by
Jacchia L.G. (1957).  I don't have a copy, but you may try and find one in
an observatory library.  If you do, I would appreciate a photo copy.  Your
study sounds most interesting.

Ed

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Edward Majden                         epmajden@mars.ark.com
1491 Burgess Road                     Meteor Spectroscopy
Courtenay, B.C.                       AMS Affiliate
CANADA  V9N-5R8                       MIAC Associate
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