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Report on the Total Solar Eclipse of 2001 June 21

by Friedhelm Dorst (Chisamba, ZAMBIA)

I have been guest of the BANANI INTERNATIONAL SECONDARY SCHOOL at Chisamba, where we had a wonderful cloudless and smoke-free eclipse of 3.302 minutes of totality.

My instruments included a Zenza Bronica 2 1/4" x 2 1/4" size camera with Kodak Provia 400 ASA film and a f.l. 40 mm wide angle lens in order to capture the whole "winter heptagon" and Betelgese in its center on one slide (only Saturn was hidden by a tree branch). Next, a digital camcorder, equipped with a 2x tele-extender recorded the event with sufficient scale and also using the "nightshot-option" for extending the visible spectrum towards IR should reveal possible structural differences in comparison to the white light corona. It also served for the above measurement of the totality duration.

Moreover I tried to secure the earthshine, but with questionable success only. This elusive feature came out on the other hand with my third istrument: a "traveler", equipped with an 1.4x tele-extender and my Nikon D1 body. Since I decided to travel without the large weight of an electrically driven telescope mount necessary for such a heavy istrument I chose a compromise: without guiding it should provide enough f.l. for more earthsine detail than the traveler photographs in Aruba (in Germany I was rained out on Aug. 11, 1999), on the other hand a 2x tele-extender would leave too less space for the inner corona. My longest exposure times were 2 seconds at f/8.3 with 200 ASA sensitivity in raw modus.

My compact flash card of 256 MB could have made 33 pictures during totality, if I would have devoted all my time for this instrument. Nevertheless I secured 26 images at 1/4000 s, 1/1000 s, 1/250 s, 1/60 s, 1/8 s, 1/4 s, 1/2 s, 1s and 2 s. Considering the atmospheric conditions my 10 exposures of 1/4 s did not suffer from image smear due to lack of a drive and consequently they can be added up after recentering with use of 2 field stars. This kind of evaluation should introduce a perfect guiding effect after all.

The corona was much brighter than 1998 and stray light intruding into the edge of the "moonface" obliterated more percentage of the limb region than in Aruba though my photos there suffered from haze-induced stray light (which remained absent on Curacao Island in comparison). I had hoped to reveal such fine details like the dark patches in Alphonsus crater or perhaps the brillant floor of the Hyginus rill, but the brightness level of the earthshine seems to have remained rather low despite of the large quantity of continental masses facing the moon during the eclipse. The 2s-frames show the familiar gross features at once yet with considerably less contrast than simple f.l. 300mm photographs of my friend Konrad Wenning who had made guided photographs with the same contrast as on Curacao but now with some stars of fainter than 8th magnitude! Nevertheless, when applying Adobe Photoshop I got tremendous detail from my surely smeared 2s-exposures. My last hope will rest upon subtracting dark images from the single shots and only then starting the adding procedure in order to remove the read-out noise of enhancing the single frames separately or their summed up image. This remains to be done.

I would like to add some facts which I heard from other people as well as some unusual reasoning about where to go best for eclipse photography. One lady of Banani International Secondary School observed the eclipse closer north to the centre line than me and told me, that she had been most impressed by the unusual calmness of nature around them when totality approached and the return of normal sound level some time after return of sunlight. Crickets were heard especially during umbral phase and also some night flowers began to emit their intense smell and stopped to continue this also after some time. Its not surprising in retrospective but I had not heard anything about those eclipse effects so far.

Watching and photographing a solar eclipse at best vision contrast was and will persist to remain a top desire for eclipsegoers with mainly esthetical motivation. Where should one recommend them to go? Go to the spot with largest solar elevation, which nearly coincides with the spot of maximum central duration! This "first glace" answer challenged me for closer examination and I found that it might prove wrong under admittedly very special conditions, the validity of whose probably nobody has investigated so far.

The sky's brightness should be proportionally dependent on the sine of the sun's elevation. The atmosperic absorption is an exponential function of the effective geometrical length of the atmospheric part of the way from the sun to us the latter being proportional to the reverse cosine (secant) of the sun's elevation. The product of these two fuctions should be a good measure of the sun-sky contrast which can be expected at different angular elevations. This functional dependence exhibits a maximum value at some 20 degrees above horizon. The corresponding value for the zenith is only slightly less in comparison. In fact this result was the reason to go to Hawaii in 1991 instead of Baja California then sacrificing nearly 3 minutes of totality. My result can only hold true, if the atmospheric clearness is optimal and of the same amount along the whole shadow track. Moreover, the cross section of the umbra as seen from the observer (and not from the moon) should be as symmetric as possible and be constant over the whole umbral path. A slightly lesser air transparence than possible will shift the best solar elevation to the maximum possible along the shadow track which was 90 degrees on 11 July 1991 due to the effect of the Pinatubo eruption which lasted for more than a year.

So, in the actually most cases the above common wisdom holds true, but, if exceptional atmospheric conditions prevail in the 20 degree section of the shadow's path, there could be found the winners. In this respect Sambia has not been a bad choice. Concerning eclipse earthshine detectibility one has to take also into account which projective continental land mass is facing the moon, if the moon's shadow is falling on bright cloud formations or on dark ocean waters and, more important than often assumed: whether the shaded umbral area is bright snow or dark Taiga forest e.g.! The actual brightness of the recent eclipse corona was not inviting so far and I expect to encounter better conditions for the solar minimum corona of 29 March 2006, when the umbra will be similarly large compared with the recent one. Last, but not least one exemple of the Zambia eclipse, exposed unguided for two seconds at 200 ASA and f/8.3 ("Traveler" with 1.4x teleconverter resulting in some 860 mm f.l.). Adobe Photoshop was applied to the Raw Image mode of a Nikon D1 camera strongly enhancing the very much lesser contrast of the unprocessed NEF image mode.



2001 Total Eclipse Photos and Reports

2001 Total Eclipse Custom Prints

Solar Eclipse Photographs

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