For years we astrophotographers have been thwarted by our recording media’s inability to capture a wide range of brightness in one exposure. A classic example is a lunar eclipse. The range in brightness between the non-eclipsed Full Moon and the part of the lunar disk in the Earth’s shadow is so great no one exposure can grab it all. You are left with either an over-exposed crescent or a dark under-exposed eclipsed Moon — nothing that looks anything like the eye can see.
At last, modern image processing comes to the rescue! This is a stack of 9 exposures, from 1/125th to 2 seconds, all at f/6 with a 130mm apo refractor and Canon 7D camera. The images were stacked and merged into one “high dynamic range” image using Photoshop CS5, whose new HDR mode is wonderful! A little tweaking of settings in the Tone Mapping dialog box, and voilá! An image of the partially eclipsed Moon that really looks like what the eye saw. I’m impressed.
— Alan, December 2010 / Image © 2010 Alan Dyer
The Amazing Sky 