Re: Strange Streak in Australia

From: Mike Monett (no_at_spam.com)
Date: 12/08/04 

Date: Tue, 07 Dec 2004 20:57:57 -0500

Ian Stirling wrote:
>
> John B?ckstrand <newsmdhmajs.100.sandos@spamgorumet.com> wrote:
> >
> >> Not very convincing. The streak is constant density all the way across
> >> - looks digitally added to me.
> >
> > NASA prankster? Not likely, imho. There are literally tons of possible
> > _natural_ explanations for this one. The small flash looks alot like
> > something produced in the lens, but the streak I have no good
> > explanation for. An insect flying by the camera would likely explain
> > this though, someone on slashdot said the EXIF says flash was fired
> > (why? No idea), so the flash combined with a insect zooming by would
> > explain it, however the streak is much too straight to really look like
> > the path of a flying insect. The flash could probably kill small insects
> > that are too close to it, Ive scarred plastic stuff by holding them
> > infront of the flash, on the other hand the flas seems to be fired in
> > the lowest position.
> >
> > There are lots of other possible causes: blowing bulb, shadow from a
> > jetstreak (both?) or a actually, why not a meteor? :)
> (some snipped, exif data)
>
> Tag |Value
>
> Manufacturer |Canon
> Model |Canon PowerShot G3
> Exposure Time |1/19 sec.
> Aperture |f/5.6
> Exposure Bias |0.0
> MaxApertureValue |73/32
> Metering Mode |Pattern
> Flash |Flash fired, auto mode, red-eye reduction mode.
> Focal Length |9.1 mm
>
> Ok, so the shutter is open quite a long time.
> 1/19th second.
>
> Apature I make as about 2mm.
>
> At the shutter speed of 1/19th of a second, the flash is
> quite adequate to freeze motion.
>
> I'm assuming that the camera fires the flash first.
>
> Just to the right of the streetlight, and extending up and down, I
> see a ligher area that seems to have two "arms" pointinf up-right and
> down-left.
> This seems to continue over the light, being washed out by it,
> coming to an end just after the light.
>
> It's interesting that approximately normal to the 'arms', and in
> line with the extended blob centered over the light is the rest
> of the streaks path.
>
> Let's assume it's an insect.
> It was happily flying past (climbing, or descending if the flash
> fires last) when the flash went off as it started to bring
> its wings down, and the flashes light ended with the wings in
> the down position.
>
> I make the angular size of the main bright spot (call it the body)
> 18 pixels across or so.
> This is about 1/100th of the picture size, which I make at about
> .1r.
> So, call it a milliradian.
> So, the 'true' size might be half a milliradian, or if the insect
> is 1mm across (apature 2mm) maybe a meter away.
>
> Say the streak crosses a third of the picture, so that's .03r/.19s,
> or .15r/s, or (if a meter away) 15cm/s.
>
> Not an extreme speed for an insect.
>
> Apature is 2mm, so assuming that it's well inside focal distance,
> and the size is 2mm (the blur is not very sharp edged),

Very good!. Sounds quite convincing. You might post your analysis in the
APOD forum at

  http://bb.nightskylive.net/asterisk/viewtopic.php?t=249

Best Wishes,

Mike Monett

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