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December 4, 2002 Solar Eclipse Expedition
Report On Sunday Morning, December 1 we
departed Hazyview in the South of the Kruger National Park and enjoyed a spectacular drive through mountains
into North-East South Africa. We arrived in Messina late that afternoon. Temperatures rose along the way.
18 degrees C when we departed Hazyview and 38 degrees C in Messina! Monday, Dec. 2
dawned cloudless and very hot. Seemed as hot as Mauritania in '73. We were
hosted in a private residence in Messina and setup our instruments in the
backyard. Private and secure with a 7' masonry fence surrounding the yard.
Alignment went smoothly and Monday afternoon we drove 12km to the Zimbabwe
border and looked across the bone dry Limpopo river. Apparently this region,
including Zambia is experiencing a severe drought. Tuesday morning dawned clear again, but one could see distant
clouds on the Southern horizon most of the day. Eclipse morning, I arose at 3am
local time (GMT +2:00) and observed dark southern skies. In this town with a few
streetlights I could see + 5mag. Magellanic Clouds are always a special treat to
observe. By 4am I could perceive that clouds were obstructing large areas of the
sky, and by sunrise the sky was 50% scattered. Things kept getting worse and by
first contact (7:12am) things looked bad., ~80% scattered. The sky looked bleak
until ~8am when a few openings appeared. I was able to track and set drive rates through the holes that
passed our way. The final 15 minutes before second contact things began
improving and totality was observed through a hole that passed our way just at
the right moment. There were 2 levels of clouds. High cirrus drifting to the
North and low running scud coming from the ENE. Totality was predicted to last
68s in Messina. I ran a sequence of 5 exposures with the Newkirk camera. 2, 5,
40, 10 and 1seconds. Only towards the end of the 40s exposure did I observe some
very tenuous low clouds moving into the field of view and they were so wispy
that I decided to continue the exposure rather than cut it short.
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Newkirk Camera Images
The above images are a collaborative effort of Wendy Carlos and myself. See her Eclipse page for a description of her work. The NEWKIRK camera which Jonathan Kern designed and built to obtain these images uses a 4" quartz/fluorite doublet of 60.25" f.l. fed by an 8" quartz coelostat. Below are unprocessed exposures obtained through the radially symmetric, neutral density filter located in the focal plane which compensates for the steep decline in coronal radiance with increasing distance. (the NEWKIRK filter, after Gordon Newkirk, former director of the High Altitude Observatory). It is fabricated by evaporating a metal film onto glass in a high vacuum. The basic requirement of such a filter is that it compensate as accurately as possible for the radial decrease in brightness as one goes away from the limb of the sun in the film plane of the telescope. Thus, the transmission should vary as the reciprocal of the function describing the K+F+sky brightness. This calls for an optical density of 10 -3 at the limb (10 f/stops, or a factor of 1000) decreasing very rapidly to a density of near unity at 4 solar radii. (See curve) The solar image at focus was .570" in diameter. The plate scale is .0175"/ minute of arc, yielding a photographic field of 2.12 by 2.68 degrees on 120 format roll-film (image size 2.23" x 2.81") . The central spot you see in each image is the calibration window, which remains centered on the sun. Because there is perceptible motion of the moon with respect to the sun, the NEWKIRK filter may appear decentered. It is not. North is up. Click on each image for a full screen view |
