Solar Eclipse Composites: 1991 Eclipse

Copyright Benjamin Gomes-Casseres 1998

The three images that follow were taken on Kodachrome 64 at the prime focus of a Takahashi FC-76, 600mm, F/8 refractor in La Paz, Baja California (Mexico) on 11 July 1991. The fourth image is a composite of these three, following the methods described in Gerald Pellett, "Eclipse Photography in the Digital Age," Sky and Telescope, January 1998, pp. 117-120. Digital processing involved first sharpening the coronal structures with a radial-blur filter, then brightening these structures by multiplying with the original images, adjusting color and contrast, and finally adding the images. The intent of compiling the images in this way is to approximate better the visual appearance of the eclipse and to show greater detail in coronal structures. This is my first attempt using this new technique and I only used three images; further improvements in the composite image should be possible by adding more images.

Fred Espenak also followed Pellett's techniques to produce a stunning image of the 1995 eclipse in India. Earlier, Wendy Carlos had done pioneering work along these lines using darkroom techniques. Her page contains an interesting comparison of coronal structures in many recent eclipses.

1 second exposure at 11:51 a.m.

1/15 second exposure at 11:50 am

1/500 second exposure at 11:50 am

Composite of 1, 1/15, 1/500

Following is an alternative representation of the corona that is not visually realistic, but that shows more details of coronal structure than does the composite above. It is the composite of the three filtered images without the multiplication step intended to brighten the images.

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