HDR Moon

Generally speaking, the Moon has an albedo about that of black coal. But it does have a surface littered with different mineral  structures and deposit and thus, much dependant uppon the the incident angle of Sun rays, the Moon does show subtle variations in colour across its surface. These colours are usually quenched in the overall overwhelming glare of the Moon. Although the albedo is like that of coal, the contrast to the surrounding sky is too much for the human eye to discern the faint play of colours which we see best - if at all - when the Moon is low in the sky where Earth's atmosphere weakens the glare of the Moon.

But camera sensors have a different perception of light and brightness so, could we use Hygh Dynamic Range (HDR) techniques to bring forward colours on the Moon?



The anwer is yes - - - sometimes - - - if you excersise great care and have a good deal of luck too..........

HDR doesn't work too well in lunar photography because even the tiniest blur due to less than perfect seeing and even the smallest effects of field rotation will be magnified in HDR images. Therefore, very good seeing and stacking of a number of series of images with varying exposure times are prerequisites to successful attempts at lunar HDR photograhy.

And then, they are prerequisites but not guarantees. One can never decide that tonight I will do some HDR photography of the Moon. One can only decide that tonight I shall TRY to do that.

My successes are limited so far. They can be counted on some three fingers, but on the night between 20 and 21 March 2011, where the Moon was at closest approach to Earth and everybody were pointing their cameras at the Moon, I decided to try to get something different to show. Thus, with a Meade LXD-75 equatorial mount, a Pentax K200D DSLR, a Tamron Adaptall-2 SP 300mm f/5.6 lens (Model 54B) and an SP F-series 2X teleconverter i took series of some 6-8 images at 1/125s, 1/250s and 1/400s at ISO 500. These series were individually stacked in Registax, the stacks then carefully aligned, cropped and merged as an HDR image in PhotoImpact. It further took a good deal of work in curves and levels and applying some pseudo LRGB techique before colours finally emerged.

Now, move your cursor over the image (single exposure at 1/125s) to see the effect of stacking and click on image to see the final outcome.

Do note, that no coulours have been added to or painted on this image - only enhanced using standard enhancement techniques. One might argue that the HDR Moon is un-natural and not worth the effort, but that is not an appropriate view. The goal is not to produce a harshly coloured Moon but to bring forward that subtle detail that can otherwise be so difficult to record, especially on the Full Moon. What you see is rather like a colour coded contour map of the Moon - only, the colours came from the Moon itself!

And, finally, it was simply great fun to make that image!!!






Copyright 2012 - Steen G. Bruun