Re: [TCML] flourescent light trick (streak cameras)

["Peter Terren" <pterren@xxxxxxxxxxxx>]

I am a rotating mirror guy (Terry Fritz, our last moderator is the other 
one).
You use the best camera you have. I use a Nikon D70s digital SLR. The thing 
is the spark is the sub microsecond event and effectively is an 
instantaneous event and is imprinted on the camera (CCD or film). An event 1 
microsecond later, like another identical spark, will be in a different 
place. Shutter speed can be seconds to catch the increasingly rare event of 
a spark as it "flashes by"
I was able to achieve 100ns per pixel so seeing events at 200kHz (like a TC 
running at 100kHz) were easy. I guess the interesting information is that 
streamers ring up and sparks ring down. Spark growth can be seen in 
streamers as well.
http://tesladownunder.com/HighVoltage.htm#High%20speed%20spark%20photography

Peter

----- Original Message ----- 
From: "Tim Meehan" <btmeehan@xxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, November 19, 2007 4:33 AM
Subject: Re: [TCML] flourescent light trick


> For all of you rotating mirror guys - what do you use to look at the 
> spark?
> Do you use CCD cameras or do you have access to some high speed film?  I
> have seen some of the older film-based high speed rotating mirror cameras,
> and there was some apparent effort put in to replacing the film frames 
> with
> inexpensive CCD chips.  I have no idea how they avoided the mirror motion
> blur on the older cameras.
>
> With a large enough radius from the mirror to the CCD chip (and a bright
> enough light source) you could probably get pretty short time windows on 
> the
> sparks, and with CCD chips/cameras you could afford to take many pictures 
> to
> get the shots you want of the breaks in the arc, which would be very cool.
>
> On Nov 17, 2007 11:06 PM, William Beaty <billb@xxxxxxxxxx> wrote:
>
> > On Wed, 14 Nov 2007, Chris Swinson wrote:
> >
> > > One thing I noticed with flu-tubes, that if you walk away from the coil
> > > slowly, it goes dim, but just before it goes out totally the light
> > > alternates inside the tube, such as 1" on, 1" off.. all the way up the
> > > tube..
> >
> > That's called "positive column striations," and fluorescent tubes always
> > have them all the time... but usually they're vibrating back and forth 
> > too
> > fast to notice.   If you have a straight piece of clear neon sign tube,
> > and sweep it rapidly back and forth while lit, then you can see the 
> > moving
> > patterns.  They're also called "jellybeans" by neon sign makers.  With
> > just the right gas mixture and high-freq power supply you can create
> > stable ones in a neon sign, so the sign is made of "dotted lines."
> >
> > I wonder if sparks at one ATM also have them.   If the blotches are 
> > moving
> > around fast, we might never realize that they exist.   (View sparks with 
> > a
> > spinning mirror and look for swerving stripy patterns.)
> >
> >
> >
> > > always thought that was pretty neat! never understood why it would
> > > light up alternate inches in the tube though!
> > >
> > > Chris
> >
> >
> >
> > (((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))
> > William J. Beaty                            SCIENCE HOBBYIST website
> > billb at amasci com                         http://amasci.com
> > EE/programmer/sci-exhibits   amateur science, hobby projects, sci fair
> > Seattle, WA  425-222-5066    unusual phenomena, tesla coils, weird sci
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