A Report by Eric H.Strach, F.R.C.S., M.Ch.Orth.,
I have first seen them at the eclipse of 1976 in Zanzibar. At
that time Graham Broadbent constructed a special screen which he
erected so that the rays fall vertically on it. It was an early
morning eclipse, the sun and moon were only 8° above the
We have seen the bands on several subsequent eclipses but failed
to record them on photographs or cine films. After Graham left
our society I tried to continue his work and inherited his shadow
band screen, and took it to Java in 1983, to Sumatra in 1988 but I did
not succeed to record the bands. In 1990 was clouded out in Finland.
I had better luck on 11th July 1991 in the Baja peninsula: I
mounted the camcorder to a fitment beneath the apex of my tripod
so that it pointed downwards to the ground, where the screen was
placed at this mid-day eclipse with the sun almost overhead. The
bands were seen but only with the eye of faith could one possibly
make out the bands in the recording and I was never convinced.
I had to miss the next three eclipses but I tried the experiment
again at Knipbaai Beach in Curacao on 26th February 1998. The sun was
again high at the time at an altitude of 60° so I used the same
arrangement. The bands were clearly seen by most observers and
I just hoped that my new camcorder fitted with a "high 8" video
cassette will succeed.
The camcorder was started 4 minutes before second contact and a
one second time generator gave signals which changed pitch every
half-minute. Thus the signals and any comments were recorded for
later analysis. I used a polaroid filter combined with an UV filter. My recording
was stopped some 4 minutes after third contact.
I suppressed my curiosity and refrained from playing back what I recorded. Only on the day after arriving home did I play back the video and there was no doubt whatsoever that the shadow bands were there, visible for 32 seconds before totality and 27 seconds after totality. However, the bands remained visible for over one minute.
They moved rapidly across the screen in a direction from E to W
before second contact and from NNE to SSW after third contact.
The bands were disposed at an angle of 70° to the E-W line
before 2nd contact and at 30° after 3rd contact - as
illustrated in the diagram.
Slow motion studies of the video showed that the bands merged at
times and on occasions they seemed to move in opposite
directions, undoubtedly a stroboscopic effect.
The question arises why I succeeded this time and not on any
previous attempts. Perhaps the use of the polaroid increased the
contrast, I doubt whether the UV filter had a similar effect. The
most probable explanation is that the bands were more pronounced
this time. Further attempts should be made to record these bands in the
future but it may take several eclipses and thousands of miles
of travel to get results. It would be far better to have a
battery of like-minded observers who would use different systems
and filters to establish the optimal method.
The images display on this page were obtained by a frame grabber and were then image-processed. My grateful thanks for their help in this process go to Mr Andrew Trafford of Liverpool University and to Gerard Gilligan and Robert Johnson of Liverpool Astronomical Society.
This page was last updated on March 24th 1998.
Please contact Gerard Gilligan.
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