[Laser] Sky illumination experiment

[John McNulty]

LOL ;-) normally 'laugh out loud', but perhaps 'light out loud' in this
case. I love the way this thread is going...

Please have a look at Fizeau and Foucault.
Fizeau devised a spinning toothed wheel assembly to modulate light (chop it)
so he could estimate the propagation of light.
<http://scienceworld.wolfram.com/physics/FizeauWheel.html>
Read our devilishly clever Tasmanian's (Chris Long) web pages, add a Bell
photophone. and bingo - those pioneering chaps could have done it way back.
Ah, but they didn't have computers or tronix. Seriously though, it's good to
see history repeating...

Keep up the great work!
73
J McN


On 7/7/05 17:51, "Laser @ KatHouse1.com" <laser at kathouse1.com> wrote:

> I built something like this many years ago but for another purpose.  I
> wanted a cheap strobe type lighting effect for use at dances.  (This was
> back in the 60's and I didn't have access to electronic strobes.)
> 
> What I did was cut a circle out of some scrap wood then mount it on the
> shaft of a motor.  There were two circular holes cut in the wooden disc near
> the perimeter but opposite each other to maintain balance of the disc.  The
> holes were the diameter of a 150 watt reflector spot light.  It worked very
> well.
> 
> I see no reason why more holes could not be spaced around the disk to reduce
> the speed of the motor for a given frequency.  If the open to blocked light
> ratio is chosen properly it should be possible to get something very near to
> a 50% duty cycle and since the light does not come on or go off all of a
> sudden it might even approach a sine wave!
> 
> Spining any kind of object with any mass at high speed can be somewhat
> dangerous.  It can even fly apart if the speed is high enough.  The more
> holes idea might be a wise one to keep the speed (and mass) reasonable.
> Keeping the signally frequency low would also help.  Just remember to BE
> CAREFUL and give some thought to the amount of mass you are spinning around
> at high velocity!
> 
> Something like this could be easily adapted to use IR by putting an IR
> filter on the light source as regular light bulbs spit out quite a bit of
> infrared.
> 
> The IR filter would be required in my case as I live in a dark sky area
> which is why all the fuss about light pollution.  The fine is $1000 for each
> occurance or 30 days in jail!!!
> 
> =====
> 
> ----- Original Message -----
> From: <F1AVYopto at aol.com>
> To: <laser at mailman.qth.net>
> Sent: Thursday, July 07, 2005 3:39 AM
> Subject: Re: [Laser] Sky illumination experiment
> 
> 
>> 
>> Hi  all
>> May be  a simplest system could be used.
>> Why not  a simple mechanical rotating shutter associates with a powerful
>> halogen  lamp?
>> A  synchronic motor powered by a simple audio amplifier with an up
>> transformer  should be adapted.
>> One can  find 240 V small synchronic motor in all the low cost AC
> automatic
>> timers.
>> A PC  with LASERSCATTER or JASON in the 70 to 90 Hz range should drive the
>> motor.
>> 73 de  Yves
>> _______________________________________________
>> Laser mailing list
>> Laser at mailman.qth.net
>> http://mailman.qth.net/mailman/listinfo/laser
>> 
> 
> 
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