RE: High speed Tesla spark photographs

["Tesla list" <tesla@xxxxxxxxxx>]

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

Fres is shorthand for the resonant frequency, of the coil.  Coilers tend
to take many liberties with shorthand use;-)

The reason for the rotating mirror is that within the span of one
"bang", there are apparently several discrete spark events, separated by
1/2Fres.  We're interested in seeing the sequence and progression of
spark geometry between each of these events.  If we didn't use a
rotating mirror, all of these events would be largely superimposed and
we couldn't differentiate one event from the others.

Have you ever seen those LED gadgets sometimes at science museums?  At
first glance it looks like a vertical column of LEDs, but if you sweep
your eyes horizontally, you see that there is in fact an image or text
sequence modulated into the LED column.  If you didn't sweep your
glance, you wouldn't see the image.  Same with the streak camera.

Regards, Gary Lau
MA, USA


> Original poster: Russell L Thornton <Russell.L.Thornton@xxxxxxxx>
>
> Thanks Gary and Terry.  I am a little more informed but just
> barely.  Gary, what is a FRES?  I could not find a def that fit on the
web.
> Also, I can see a little better why the streaking is minimal.  I
> think you are assuming that you are catching just one spark strike
> since more than one in a single pass of the mirror at 5000 RPM ( =
> 1/83 second shutter speed) would show parallel sparks along the
> smear.  I have seen photos of lightning where the camera is
> rotated  in azimuth during a single exposure and the film captures
> multiple strikes.  That being the case now that you have convinced
> yourself that at a single mirror RPM of 5000 delivers you a single
> strike the shutter speed is now basically somewhere between 1/60 and
> 1/125.  Why don't you just shoot direct and eliminate the mirror and
> smearing? Or am I still confused?
>
> Russ
>