(meteorobs) OT -Stuart et.al., Another visit on issues. Re: Thomas's fireball reference.

[Larry]

I too am having 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 emission from this fireball in 
flight.

Notably the smearing is absent at or near the base of the outjetting 
streams. Smearing should have occured if there was any kind of *oblique 
tumble. (* Needed to account for differing upper and.lower stream 
curvatures.)

The same lack of smearing coupled with apparent stream curvatures in 
opposition did not match conventinal fireball ablation or other photographs 
and forum presented arguments.

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 not the lack of smearing at the BASE of each point of fireball 
plume(?) emission. Each appears sharply defined and separated.

Canon appears to be a part of the answer.

First of all, Canon Mfg. informed me that this camera would take 2 full 
frame captures of 15 seconds each for every 30 second timed shootings. A 2 
minute time shot would contain 8 full frame electronic captures.

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 suggests it occured in the 7th, or more likely midway in 
the last (8th), 15 second full frame capture.

The 20D also has a special IR filter which makes all of its pictures look 
the same as it would look to a human eye!  This CMOS camera heavily filters 
out IR. The heat smears we normally would expect to see from a fireball 
ablation photograph will not be present. This also accounts for the extreme 
sharpness and resolution right down to the needle-like  fireball tail.

I do not know if we can be certain on the size(mass) of this fireball 
especially since this camera usually came with a 55mm lens.

Now guess where I am going........... Either this fireball with standard 
ablation characheristics zipped down on an oblique angle after "lingering" 
in a circular wind stream for a few seconds........ :-)

Or..... it zipped down tumbling on an oblique angle relative to the camera.

Larry
YCSentinel