A crescent moon in deep twilight is analogous to shooting the eclipse. The exposure difference from bright crescent to earthshine dark side is about 10 stops and the sky brightness will be similar to totality. The best time to try this image is 30 to 90 minutes before/after sun rise/set during the 3 days before/after a new moon. A crescent larger than about 10% will blow out the image of the earth facing dark portion of the moon.


Between now and the eclipse, there will be opportunities to do this during

April 23-28

May 23-27

June 21-26

July 20-25


I suggest you try exposures 1 EV apart from 1/2000 sec to 4 sec at f5.6 and ISO 400 or equivalent. That is a 14-stop range to account for the variability of sky brightness during twilight. You will not need all these captures but by using the full range, you’re more likely have all the ones you need.


The images will need to be post processed in a capable HDR program. I’ve seen success from Easy HDR, Photoshop HDR Pro 32 bit and Photomatix but try what you already have first.   There are two big challenges in post processing: getting needed contrast in the dark portion of the moon without causing excessive blooming around the bright side and getting gradual tonal gradation in the margin between light and dark without artifacts. Some deal with these challenges by using layer masking techniques and specialized stacking software to pre-process images before applying HDR processing:  http://astronomy.robpettengill.org/daylapse.html


Without a tracker, exposures longer than about 1/4 sec will blur noticeably when longer focal lengths are used due to the earth’s rotation. So this practice will give you a good idea of how slow you can go. Try using higher ISO to gain brighter images with shorter shutter speeds.


Exposure Settings

(or Equivalent):

F 5.6
ISO 400
One comment on “Crescent Moon HDR is Great Practice for Eclipse
  1. DaveHorton says:

    Great info Terry!

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