The Great American Solar Eclipse 2017
Total Solar Eclipse, 21 August 2017 17:23 UT, from John Day, Oregon, USA


Click here for an animated GIF of the eclipse progressing: Animation Click here for a composite photo of all phases of the eclipse: Composite


Sun: Our sun has a mean distance from earth of about 93,000,000 miles, and a diameter of about 864,000 miles (a little more than a hundred times that of Earth). Our moon has a mean distance from earth of about 239,000 miles, and a diameter of about 2160 miles. Fortuitously, that geometry results in the angular size of the moon, seen from the surface of the earth, being almost exactly the same as the angular size of the sun, seen from the earth. So when the new moon aligns perfectly with the sun and the earth, the moon casts a shadow to a small patch of the earth's surface, blotting out the sun for those fortunate enough to be inside that shadow. When that happens, the sun's corona (which is much less bright than the sun, and cannot be seen while the sun is shining) becomes visible. It is an amazing thing to see!

I was fortunate enough to be in central Oregon for this event, and photographed the progress of the eclipse.

For the sharp-eyed who spot a small dot below and to the left of the ball, that's the bright star Regulus, which (along with a few other bright heavenly objects) showed to the naked eye during totality.

Technical Information:

The totality/corona image is a stack of 5 images: 1/8 second, 1/13 second, 1/30 second, 1/60 second and 1/125 second. The GIF is a stack of 39 images, including the totality image.

Equipment: The filtered images of the eclipse's progress were taken with a Canon 5DSR, wearing a Canon 500mm f/4L IS lens plus a Canon 1.4xIII focal extender. A Thousand Oaks solar filter was used as the filter. The corona images were taken with a Canon 5D Mark III, wearing a Canon 100-400 f/4.5-5.6L IS II lens, at 400mm.

Processing: No calibration performed. Corona images were processed initially in Adobe Bridge, then stacked and manually aligned in Photoshop CC2017, with a good deal of other things done to the data in Photoshop. The filtered images in the GIF (the orange ones) were manually aligned in Photoshop CC2017, then turned into an animated GIF in Photoshop. The composite photo contains some of the same images used in the GIF; I used Photoshop CC2017 to put them all into one photo.

Location: John Day, Oregon, USA

Date: Data acquired from 16:08:30 UTC through 18:44:58 UTC, 21 August, 2017; image posted August 25, 2017

Copyright Mark de Regt, 2017