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

Re: Skylab 3

From: Martin Shough <parcellular.nul>
Date: Mon, 10 Dec 2007 15:57:19 -0000
Archived: Mon, 10 Dec 2007 14:14:10 -0500
Subject: Re: Skylab 3


>From: Bruce Maccabee <brumac.nul>
>To: <ufoupdates.nul>
>Date: Sun, 9 Dec 2007 17:10:06 -0500
>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

>>>From: Bruce Maccabee <brumac.nul>
>>>To: <ufoupdates.nul>
>>>Date: Fri, 7 Dec 2007 12:12:58 -0500
>>>Subject: Re: Skylab 3

>>>However, to have image extension that is "left-right" as well as
>>>"up down" one needs more than just one axis of motion. In this
>>>case one needs two axis motion and that requires accelerations
>>>to change the rotation from around one axis to around another,
>>>perpendicular axis, and that results in "loopiness" of the
>>>photo. I should point out that in "loopy" motion one often gets
>>>bright spots which signify (if the light itself is constant)
>>>momentary slow-downs or stops in the angular rotation (bright
>>>spots imply longer exposures at various portions of the
>>>"loopy" image.

>>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?

>Not likely. First, there is a restoring force: the hand.

>The photographer tries to steady the image by applying a force
>(torque) opposite to the direction of motion (rotation). This
>is quite independent of gravity unless the lens on the camera is
>large enough to have a noticeable torque that tends to pull the
>lens downward (main body of camera held by hands, of course).

>Removing this downward force on the lens (no gravity) would not
>remove the hand vibration and the continual attempts to
>compensate.

Well this is more or less what I meant. Perhaps I should have
been more explicit. I didn't mean to imply that there would be
no restoring forces at all, but only there is no _gravitational_
restoring force. This being so, the wander of the camera axis
will be subject only to those forces other than gravity that may
affect its path. Just as you say. My conjecture is that the path
in these circumstances could possibly be less loopy. I'm not
sure this is refuted above.

>Also, if the shutter time was 1/250 of 1/500 sec there likely
>wouldn't be time for hand vibration to switch from up-down to
>left-right. If there were noticeable smear it would be a short
>unidorection smear resulting in changing a perfectly round dot
>to one elongated ina single direction.

I don't necessarily disagree, but I suppose the "likely" here is
the word that needs qualifying by some kind of experiment or
calculation just in order to rule it out.


Martin



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