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Location: UFOUpDatesList.Com > 2007 > Dec > Dec 10

Re: Skylab 3

From: Bruce Maccabee <brumac.nul>
Date: Mon, 10 Dec 2007 11:45:36 -0500
Archived: Mon, 10 Dec 2007 14:24:22 -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

snip

>>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?

>It may not be appropriate to consider gravity a "restoring"
>force in this context, as it suggests that gravity tends to
>return the camera axis to the desired alignment. This would only
>hold in the case of a camera that is pointed straight down.

>Aside from that nit, I find plausible the idea that the
>'trajectory' of the camera aimpoint would differ in a free-fall
>environment, perhaps even to become more linear, as Martin
>suggests.

>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
camera.

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
steady.

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
be!




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