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Location: UFOUpDatesList.Com > 2007 > Dec > Dec 11

Re: Skylab 3

From: Brad Sparks < RB47x.nul>
Date: Mon, 10 Dec 2007 21:32:42 EST
Archived: Tue, 11 Dec 2007 18:16:35 -0500
Subject: Re: Skylab 3

>From: Bruce Maccabee <brumac.nul>
>To: <ufoupdates.nul>
>Date: Mon, 10 Dec 2007 11:45:36 -0500
>Subject: Re: Skylab 3

>>From: Michael Tarbell <mtarbell.nul>
>>To: ufoupdates.nul
>>Date: Sun, 09 Dec 2007 12:22:53 -0700
>>Subject: Re: Skylab 3

>>>From: Martin Shough <parcellular.nul>
>>>To: <ufoupdates.nul>
>>>Date: Sat, 8 Dec 2007 14:57:39 -0000
>>>Subject: Re: Skylab 3


>>>Just a thought: Is it possible that the characteristic looping
>>>returns of the light trail in normal camera jitter are partly
>>>due to gravity? In free fall there is no restoring force, so
>>>excursions of the camera off-axis will perhaps not be self-
>>>correcting in quite the same way. Could this lead to more linear
>>>and less loopy-looking trails?


>>If such was the case, it would not eliminate the 'bright spot'
>>issue that Bruce alludes to, and indeed would exacerbate it. A
>>human being would not be capable of hand-reversing the linear
>>course of the camera at constant angular rate, and indeed this
>>would be difficult even with mechanical assistance. It seems
>>unavoidable that the linear segments in the image would have
>>tell-tale brightened end points. But this is just what is seen
>>in the fourth photo!

>>So, it may be prudent to ask, what is the minimum time required
>>for a human hand to execute three out-and-back linear 'jitters'
>>of some tenths of a degree in angular width? And, is the
>>corresponding shutter speed consistent with any plausible
>>configuration of the camera at the time (lens size, f-stop, film
>>speed, etc.)?

>As I pointed out in another email, the loops and "whorls" I have
>seen (where the hand reverses the vibration direction to
>recenter the image) have occurred over the time of several
>frames of a movie or video.

>Typically any given frame (1/30 sec) or a still picture (1/60
>sec or less) will have only a straight or a bent image (of a
>distant light, for example).

>The characteristic restore time (to bring the image back to
>center) depends upon the person (who is holding the camera), how
>he holds the camera and the mass and moment of inertia of the

>All these things work together to make the hand vibration time
>many tens to hundreds of milliseconds, I would say from the
>experience of looking at numerous videos and movies. I have not
>tried to prove this by experiment. Of course, anyone is free to
>take a camera with 1/250 shutter time and take a picture of
>distant light - 'point source - while trying to hold the camera

>My bet is that the image will be quite close to the actual shape
>of the object/light with no more than a slight smear in one
>direction... I won't try to predict which direction that would

As I calculated for a previous posting, if the camera smeared a
single dot image into a nearly 1 mm Y-shape image and if the
exposure setting was 1/500 second then the camera would have had
to move at roughly 500 mm per second or roughly 1 ft/sec and it
would have to stop and reverse motion perfectly in the opposite
direction at 1 ft/sec back down one branch of the crooked Y-
shape then go back up the other branch at about 1 ft/sec.

For comparison with a known and widely available example of
handheld photography there is the famous Zapruder film of the
JFK assassination. In the stabilized version one can see and the
handheld motion from frame to frame and it is no more than about
1 mm per frame and usually only aboit 0.2 mm per frame.

At about 18.3 frames per second this is at most only about 18 mm
per second camera velocity, not even close to the Skylab 3
photo, assuming the fourth photo is blurred due to camera
motion, and that it is on the order of about 500 mm per second
camera motion. Thus about a 1/18 second exposure is long enough
to capture a 1-mm camera jitter blur of an object, but not a
1/500 or 1/250 second exposure, in which case the jitter would
be 10 to 30 times too small to explain the fourth Skylab 3

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