Wednesday, 25 April 2012

Less than a month to go before the Annular Solar Eclipse across parts of China, Japan, and the USA. The general rule of thumb in eclipse chasing is that a total is worth any effort, an annular is worth a short trip, and a partial worth setting up in the yard. So for this eclipse, we make a short trip. Out to California to join some fellow eclipse chasers.

An annular solar eclipse is a great practice for a total solar eclipse photography. Rare events that provide a sharp contrast across the solar disk are wonderful. Time this just a few short days before the Transit of Venus and we have a "must photograph" situation in my book.



I am considering the use of my Coronado 40mm hydrogen-alpha telescope. To image I need to use the 2x barlow and negative projection. This fills the image frame nicely. Testing this set up produced nice images with exposures of about 1/60th of a second on up. Longer exposures (over 1/4 second) shows prominences around the edge of the photosphere. The longer the exposure, the more prominences that showed up in the images. For this configuration, tracking is essential at exposures over a quarter second. For more details about whether you need tracking (or not) see http://www.eclipse-chasers.com/Photo9.html

After a lot of dump shots, I got a few that took to the computer and tried to merge with Photoshop. There are a couple of things to note. The above image consists of two images laid on top of each other. The grey image is the shorter exposure. I colored it grey. The color of hydrogen-alpha is a deep red, more like the outer image which is a clipped with a black circle and placed behind the grey image.

A couple of things I learned are that I need to account for the solar disk darkening about the edges by adding more images with exposures in between the extremes. This is will be difficult as the solar disk has low contrast and will fade out as more images are added - more fun with Photoshop awaits!


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