Thanks for the opportunity to write. I began filming meteor impacts
on the moon in 1997 using CCD cameras and long-pass near-infrared filters.
I was successful during the Leonids of 1997 in capturing several images
of the impacts on video -- some simultaneous. For a while, I had posted
them on a website, but they drew no great attention. Since then, I have
developed several smaller camera systems for imaging in the NIR portion
of the spectrum between 850nm and about 1100nm. What I have found is that
electronic noise lasts, at most, 2 video frames. I have been able to see
impact flashes lasting between 30 and 45 video frames by using the NIR
portion of the spectrum. I published a couple of articles in the Northeast
Florida Astronomical Society newsletter (Skywatch) regarding my findings
and the methods of constructing NIR CCD systems. The advantage is that
I can make observations in daylight without much interference from the
sun. The original video was obtained using a 1! 50mm f/13 refractor located
in Jacksonville, Florida. I have also used wide field optics, a Schmidt-Cassegrain
and even a Dobsonian system for this type of imaging. I am currently trying
to develop a method using an intensified CCD with an integral long-pass
filter. I will be making plans with the Society here in Jacksonville for
more organized observation of the lunar impacts during upcoming meteor
showers. I look forward to reading more reports of this type of work.
My eventual goal is to be able to spectroscopically image the impacts
to see if there is a correlation between the spectral light emissions and
the compositions of the meteor and the soil where it impacts -- a kind
of remote lunar geology.
Allan Kimble
Sr. Scientist
Microscopy & Spectroscopy Laboratory
Vistakon, Johnson & Johnson Vision Care
Jacksonville, FL
Tel. (904) 443-3020
Fax (904) 443-3433
--
David Palmer
dmpalmer@mac.com
Thanks for forwarding the message from Allan
Kimble in Jacksonville, who has been on my occultation e-mail list for
a few years. His 1997 observations are interesting, but he should
have asked others to look, too; we would probably have obtained confirmed
observations that year (in 1997, I gave no thought to such observations,
and probably would have considered them impossible; I [and I think nearly
all other observers] were quite skeptical until I saw Brian Cudnik's impact
"A" flash on my videotape). Also, as
Tony Cook has found out, we need to worry about cosmic ray hits on
the CCD with sensitive cameras; especially if 2 or more "flashes" occur
simultaneously, they are probably cosmic ray hits. I'm copying this
to Tony and to Peter Gural, who will be interested in Allan's efforts,
and also to Pedro Sada (who collaborated on a Nature article with a Spanish
astronomer who claimed to have imaged a lunar meteor impact in July 1999
[but no confirmation, unlike some of Sada's confirmed 1999 Leonid impacts])
and to Laurent Pellerin, who also recorded apparent lunar meteor impacts
with a 26-inch telescope near Orlando the night before you, Sada, and I
got the 7 confirmed events in November 1999. David D.
Return-Path: <AWKimble@aol.com>
From: AWKimble@aol.com
Date: Wed, 5 Dec 2001 07:45:00 EST
Subject: Re: somebody else, claiming impacts from 1997
To: dunham@erols.com
David: Thanks for forwarding the additional information. You make in interesting point in your email regarding cosmic ray interferences. In the CCD's these particles are in fact quite effective in producing the electron-hole pairs that give rise to the signal and will look quite similar to impacts. I have found that cooling the CCD has no effect on removing them and in fact, makes them more prominent by reducing the overall electronic noise of the system. However, a clue that I have that distinguishes electronic noise and cosmic rays from true impacts is the duration of the signal. The energy of the emission spectrum of an impact is probably richer in near-infrared and infrared than in visible light. As such, a system designed to observe these portions of the spectrum will observe longer emission times, i.e., the number of frames will be greater than in the visible portion of the spectrum. Most monochrome CCD cameras today have integral IR cutoff filters. If these are removed and a long-pass filter installed (850nm -- higher, for example), the camera is then limited to observing the longer wavelengths, up to about 1100nm where silicon ceases to be sensitive. I have also begun experimentation with intensified CCD's using microchannel plates to amplify the signal. Interestingly, cosmic rays appear to behave strangely with this type of detector. After many nights of observation, I am convinced that when a cosmic rays passes through the microchannel plate, it is deflected. (Assuming that cosmic rays are charged, then this would make sense.) The resulting image looks a lot like a moth flying through the field of view, as the flash is mobile and follows a curved path on the monitor. I am also aware that the intensifier is not nearly as sensitive to NIR radiation as the plain CCD, but am working on this to see if it can be improved. As I mentioned in my original email, I had measured two nearly simultaneous flashes that worked out to 30 and 45 frames, respectively. I used Adobe Premier to analyze the original tape on an
I am hoping this observational method really catches on and have been watching with great interest all of the reports. I am still trying to relocate Walt Dobar who was a retired NASA geologist here in Jacksonville for a number of years. We worked together at Bendix Aerospace over 15 years ago, and up until recently worked on some informal projects on tektites with Jacksonville University. We lost contact a few years ago, but Walt would be a great collaborator on what additional information could be gleaned from these observations.
I am looking forward to hearing more on the subject. Thanks for promoting
the technique and keeping everyone informed. Best regards, Allan
Kimble