-------------------------------------------------------------------
Composite image of the Solar Corona during the
Total Solar Eclipse of 1995 October 24

by Wendy Carlos and Fred Espenak

The solar corona exhibits a tremendous range in brightness which cannot be captured photographically on any single exposure. Fortunately, the computer can be used as a tool to combine a series of images taken at different exposures into a single composite image which more closely resembles the corana's appearance as seen by the human eye.

This image of the Sun's corona was made from a composite of eight separate photographs made by Fred Espenak from Dundlod, India during the total solar eclipse of 1995 October 24. The photos were made on Kodak Royal Gold 100 with a Nikon FE w/MD-12 motor drive, a Sigma 400mm f/5.6 APO telephoto and a Sigma 2X teleconverter. Exposures were 2, 1, 1/2, 1/4, 1/8, and 1/15 and 1/125 seconds. After development, the images were transferred to Kodak photo-CD. Wendy Carlos then used Abobe PhotoShop and a Macintosh IIfx to combine the eight images into one composite image. 

The techniques used were orignally developed over a period of a dozen years, using traditional photo darkroom tools then available. Each images was masked to allow only that portain which contained real image data to contribute to the final composite. So the usual burned-out or underexposed coronal portions were removed. The good parts were graded to fit the dynamic range of final print materials, darkening the bright inner portions, while lightening the outer dim parts. 

These same hand-tuned processes were adapted to computer image software, with added features, like checking that the allignment between original frames is exact, enhancing low-contrast differences, and removing glitches and grain noise. It still requires many hours and a deft experienced hand to pull it off. Observing many total eclipses gives you the memory of what the desired goal ought be: a natural portrait of what your eye and brain see during totality!

Photo ©1996 Wendy Carlos and Fred Espenak

----------------------------------------------------------------