(meteorobs) Final Report on fireball.

[Chris Peterson]

> If the fireball passed through the eye of a strong CCW CIRCULAR high
> altitude wind pattern on an oblique angle of approach or recession 
> relative
> to the cameras position, the differing plume curvatures could be accounted
> for.

The fireball is luminous through a vertical distance of about 35 km. The 
angle of approach is not very oblique. These characteristics can be 
determined (within a fairly narrow range) since the speed of the meteor and 
its distance from the radiant are precisely known, and its height when first 
becoming luminous can be reasonably estimated.

> First of all, Canon Mfg. informed me that this camera would take 1 full
> frame capture every 30 seconds in timed shootings. A 2 minute time shot
> would contain 4 full frame electronic captures.

This is not correct; you have misunderstood the camera operation. The camera 
is perfectly capable of taking a single 2-minute exposure, and the EXIF 
header in the file leaves no doubt that it did so in this case. The 
30-second limitation is merely the longest internally timed exposure that is 
possible. In the bulb position, with an external release or the standard 
Canon remote control, there is no time limit. This image is a true 2-minute, 
single exposure.

> The time period of most fireballs that we record like this would probably 
> be
> about 5 to 7 seconds.

In fact, using the same geometric calculations mentioned above, it is easy 
to determine that the meteor duration was 2-3 seconds. This is also 
consistent with typical fireball durations for fast meteoroid streams. A 5-7 
second duration would require a much shallower path, and would be unusual 
for a 66 km/s stream. Such long events usually suggest a much slower, more 
massive body.

> The heat smears we normally would expect to see from a fireball composite 
> or
> timed photograph WILL NOT BE PRESENT.

I've read a lot of papers about meteors, and I've never encountered this 
concept of "heat smear". Could you please explain what you mean by the term?

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Larry" <ycsentinel at att.net>
To: <meteorobs at meteorobs.org>
Sent: Sunday, September 20, 2009 11:34 AM
Subject: (meteorobs) Final Report on fireball.


>I too have had trouble keeping the tumbling and outjetting concept 
>together.
> Details in the picture were both for it and against it. Tumbling "seemed" 
> to
> be the CLOSEST solution in solving both upper and lower stream curvatures 
> &
> the apparent periodic nature of emissions from this fireball in flight.
>
> Notably smearing is absent at & near the base of the "outjetting" streams.
> Smearing should have occured if there was any kind of *oblique tumble 
> during
> periods of jetting. (* Needed to account for differing upper and.lower
> stream curvatures.).
>
> The same lack of smearing coupled with the apparent stream curvatures in
> opposition did not match conventional fireball ablation or other 
> photographs
> of timed & composite imaging of events. Forum presented arguments were not
> comprehensive enough to solve at the same time, the stream curvatures and
> what appears to be descrete ejection or emissions.
>
> So back to square 1.
>
> If the fireball passed through the eye of a strong CCW CIRCULAR high
> altitude wind pattern on an oblique angle of approach or recession 
> relative
> to the cameras position, the differing plume curvatures could be accounted
> for. But still not accounted for is the lack of smearing at the base or
> points of stream origin. Each stream appears sharply defined and separated
> without significant smear.
>
> Canon appears to be a major part of the answer.
>
> First of all, Canon Mfg. informed me that this camera would take 1 full
> frame capture every 30 seconds in timed shootings. A 2 minute time shot
> would contain 4 full frame electronic captures. Trivia--I also read that 
> it
> takes 1 frame(part?) every 15 seconds which I believe meant combined to
> produce 1 full frame image in 30 seconds.
>
> The time period of most fireballs that we record like this would probably 
> be
> about 5 to 7 seconds. The contrast and sharpness of this fireball compared
> to the star field, and the fireballs failure to burn out or detonate
> suggests the camera concluded the last(4th) 30 second full-frame before 
> the
> fireball may have ended its travel.
>
> Results of checking the Canon 20D specifications:
>
> The 20D has a very special IR filter and processing which makes all of its
> photographs look the same as it would actually look through a human eye!
> This CMOS camera HEAVILY filters out IR and as I read it, UV wavelengths
> too, so that it records only the narrow band of VISIBLE light. Herein is 
> the
> problem!
>
> The heat smears we normally would expect to see from a fireball composite 
> or
> timed photograph WILL NOT BE PRESENT. This also accounts for the extreme
> sharpness and resolution right down to the needle-like tail on the 
> fireball.
>
> I do not know if we can be certain on the size(mass) of this fireball
> especially since this camera apparently was sold with a 55mm lens.
>
> Now guess where I am going........... Either this fireball zipped down on 
> an
> oblique angle after "lingering" in a circular wind stream for a few
> seconds..... :-}
>
> Or..... it zipped down tumbling or spinning on an oblique angle relative 
> to
> the camera.
>
> Summation of evidence:
>
> 1) Previous negative photographs.
>
> 2) UV & IR stripping of Canon 20D photographs.
>
> 3) Text contained in NASA site regarding meteor spin and jetting. See
> subject "Spinning Meteors" under 1999 Leonid MAC results. (Normal URL
> without the www stuff) .....leonid.arc.nasa.gov/
>
> I believe this should put a good wrap on Ashcrafts discovery, and ends
> further investigation on my part.
>
> Larry -YCSentinel
>
> (Hope this post got through.)