ClarkVision Photography: Astrophoto 1 Gallery

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image solar-eclipse-total-700mm-6d.c08.21.2017.IMG_0357-79c.c-c1es0.4xs.jpg is Copyrighted by Roger N. Clark,

Total Solar Eclipse in Enhanced Color, August 21, 2017

My first view of totality during the August 21, 2017 eclipse was through a 4-inch refractor (my 300 mm f/2.8 telephoto lens with an eyepiece attached to the viewfinder of the camera). As the camera took images once every 2 seconds, I had an astonishing view of the pink prominences and greenish-gray corona. Everyone should see such a sight at least once in their lifetime. The structure in the corona is mainly due to charged particles in the Sun's magnetic field. If your monitor is well calibrated, the color of the corona should look greenish-gray.

The green color is caused by iron XIV "Coronium" emitting at 530.3 nm in the green. The pink-magenta color in the prominences is due to hydrogen emission (Hydrogen-Alpha at 656.3 nm in the red, Hydrogen-Beta at 486.1 nm, blue-cyan, and Hydrogen-gamma at 434.1 nm in the blue). The colors in this image have been enhanced and contrast boosted over the natural color image.

Technical. The corona seen during a total eclipse has a very high dynamic range. Multiple exposures were needed by a camera to cover that range. I used Canon 6D 20-megapixel digital camera, with a 1.4x teleconverter and a Canon 500 mm f/4 telephoto lens on a fixed tripod. Exposures: 7 frames at 1/8 second, 3 frames at 1/25th second, 5 frames at 1/80 second, and 2 frames at 1/250 second, all at f/11, ISO 200. The multiple frames at the same exposure were aligned and stacked with sigma-clipped average and saved as 32-bit floating point images. Then each stacked image had a radial blur applied and 75% of the blur subtracted to enhance detail. Color correction were made at each step to show the colors that came out of the camera. The different exposures were assembled and levels adjusted to give a consistent flow from bright inner to the faint outer corona. Full plate scale was 1.04 arc-seconds/pixel. The image is reproduced here at 4.8 arc-seconds/pixel.

For more information on the color of the solar corona, see: True colors of solar corona by Miloslav Druckmüller

See How to Photograph the Sun: Sunrise, Sunset, Eclipses for more details on solar eclipse photography.

To learn how to obtain stunning images like this, please visit my Extensive Articles on Photography .

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