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Re: (meteorobs) Re: Some Perseid photos



At 09:39 AM 8/21/99 -1000, I wrote:

>I guess the basic question I would have is: "Did the guy that took the
>picture actually see the object that created that image on the film?"  Has
>anyone asked?  I'll e-mail him if not.
>

I decided to go ahead and ask him about the picture.  Here is Robin's reply:

Yes, there were aircraft in the area. Yes, I saw a meteor that ended in a
flair in that area during one of my exposures. It was surprisingly low and
bright. Am I positive that this frame shows the meteor I saw, not
absolutely. There were four shots taken in that direction. The last one
started at 10:32 pt Aug. 12. I recall thinking, that I had done the exposure
bracketing I wanted, and even captured a meteor. That was enough for the
east shot, now I could move the camera to shoot towards the south.

My main interest that night was to test film and exposure for some light
pollution studies. The camera was a Nikon N90 set to take 10 min. exposures
with a 20mm - 35mm f/2.8 zoom lens set to 20mm f/2.8. This is one of Nikon's
professional lenses and is as sharp as a good fixed focus 20mm lens. The
film was Kodak E200 which has been getting good reviews on APML (Astro Photo
Mail List). The location was the Monterey Institute for Research in
Astronomy's Oliver Observing Station atop 5000 ft Chews Ridge in Monterey
County, California. http://www.mira.org/fts0/mira/history/h001z.htm

The aircraft I have seen on astro photos are much fainter and show periodic
flashes as the lights blink on and off. They also enter at the edge of the
photo and either continue across the frame, or end abruptly (as the exposure
ends). I know I didn't start any of my exposures with an aircraft of such
brightness in the frame. So, the light would have had to come on during the
exposure. If they were landing lights, I would expect them to come to full
brightness very quickly (relative to the speed of the aircraft) and be
constant. I am not aware of aircraft lights that would come to full
brightness so slowly. To suddenly flair and then go out does not make sense
to me, either.

The red line emerging from the flair is interesting. If it were an aircraft
it could be explained by a constant red light. Do aircraft run constant red
lights, or do they all flash? The path of the line could be explained by a
fairly sudden drop in altitude, not impossible for a small plane coming in
for a landing.

How could the irregular path be explained if it were an ember from a meteor?
I don't know much about explosions and resultant trajectories. I can only
make crude speculations. It seems possible to me that the explosion could
send a glowing fragment slightly off of the trajectory of the meteor. How
would it then resume the original trajectory? The pockets in a golf ball
will give it lift as it spins. Could a meteor fragment attain lift in the
same way. I don't know. There does seem to be some waviness in the bright
area of the streak. Could this be caused by tumble?

Could the irregular path have been caused by a sudden movement of the
camera? That seems possible. I don't recall how close to the camera I was
when I saw the meteor, but I would guess that I made a sudden movement in
reaction to it. That could have been transferred through the floor to the
camera tripod. If it were a sudden enough jolt near the end of the exposure,
I guess, it could have affected the image of the meteor without affecting
the stars slower progression across the frame. Or, the camera could have
settled back to its original position, and the one second, or less, duration
of the jolt might not show in the stars during a 10 min. exposure.

--
Robin Casady
http://wwwdot carmelCoast.com

Casady & Greene, Inc.
http://wwwdot casadyg.com


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