Contains: Sun

Image of the day 09/07/2017

Total Solar Eclipse Enhanced Corona Detail, August 21, 2017

Technical card

Resolution: 1482x1075

Date: Aug. 21, 2017

Time: 11:47

Frames: 17

Focal length: 700


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 corrections were made at each step to show the colors
that came out of the camera. The radial blur was then applied again at 41% subtraction, and then a
third time, and each step the intensity increased with the curves tool. Finally, Adaptive
Richardson-Lucy deconvolution was applied to recover fine detail. The multiple processing steps also
enhanced the color saturation. 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 1.94
arc-seconds/pixel. The image is reproduced here at 4.8 arc-seconds/pixel.




Roger Clark


Total Solar Eclipse Enhanced Corona Detail, August 21, 2017, 


        Roger Clark