RE: High speed Tesla spark photographs

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

Hi Terry, Peter:

I'm not "getting" something.  For Peter's image
http://tesladownunder.com/HVRotMirrorTeslabigSpark1Singel.jpg

I get how each vertical trace is displaced due to the rotating mirror,
but I don't get why it's dark between each trace.  I would have guessed
that it would show up as a smooth vertical smear for the duration of the
bang.  Isn't the arc luminosity more or less constant during the
duration of a bang?  Sure, it starts at zero, increases to some peak
value, and decays, but I wouldn't guess that it oscillates from zero to
peak at Fres.

Is there some other opto-mechanical chopper in addition to the sweeping
mirror?

Also, Peter - what film speed and lens aperture did you use?  I'm
wondering if a garden-variety digicam is fast enough.  I assume the coil
operated in single shot mode?

Thanks, Gary

> At 05:54 PM 9/11/2006, you wrote:
> >I have been working on a setup to show high speed streak photos of
> >Tesla sparks. Setup is a 3000 RPM synchronous motor with a single
> >mirror which reflects the sparks image to my Nikon D70s with 180mm
> >lens. I can resolve the 100kHz ring down sparks readily with about
> >1us resolution. 1 camera pixel is 100ns. Calibration is
> >geometrically and with a LED at 100kHz.
> >With this running on a 6 inch spark to ground I can see detail of
> >the central channel of the initial spark, details of the 5 or so
> >ring down sparks, gaps in the spark channel, immediate and delayed
> >electrode ionisation effects and (I think) a spark hitting a dust
mote.
> >Photos and details here:
>
>http://tesladownunder.com/HighVoltage.htm#High%20speed%20Tesla%20spark
> %20photography
> >Terry is also working on a more advanced purpose built setup.
> >
> >Peter
> >http://tesladownunder.com
>