[Laser] Sky illumination experiment

[Laser at KatHouse1.com]

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
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>