Does the Moon have the colour it should have ?

 
 
 


May I ask for colours - even on the Moon.

Aunt 1: The Moon is white.

Aunt 2: No the Moon is yellow.

Aunt 1: The Moon has the color, moons should have!

(From "Skaermydsler" by Gustav Wied, 1901)

  

Connoisseurs of Danish author and playwright, Gustav Wied’s "Skaermydsler" (meaning something like "Skirmishes" - “Tiffs” or “Eternal small quarrels”) may recall Aunt 1 lecture Aunt 2 that "The Moon has the color, moons should have." But is this entirely true? Folks as folks are mostly like always ask for clarity and sharpness in lunar photographs and then again for a little extra sharpness and then once again for more sharpness. But what happens with the colours of the Moon?


Picture taken on 24 April 2010 with an old Olympus C-50Z 5MP compact camera

and a Tamron spotting scope (17.5X magnification). Six images stacked in Registax

and post-processed in PhotoImpact.

 

When we look upon the Moon, glaring high in the night sky, we see it mostly in grayscale and finer nuances are hard to distinguish. On the other hand, when we see it closer to the horizon, the blue light scatters more than the red and green, while at the same time the light is dimmed by the atmosphere and we see the moon in more "pleasant" reddish and yellowish hues. And it is much easier to distinguish the subtle nuances between different parts of the lunar surface in this situation.

 

One can find a fine little discussion on the lunar colours in a program for “Skirmishes” from Aalborg Theatre here:


http://www.aalborgteater.dk/Files/Bille ... ER_WEB.pdf

Can we reproduce these tones - although we cannot really see them - with digital technology? The answer is a partial “YES”. The obvious thing to do would be to use High Dynamic Range (HDR) techniques directly, but for several reasons HDR is not so suitable (or easy) for lunar photography. HDR images of the moon usually turn out rather blurred for a number of reasons. HDR is very sensitive to the minute changes from image to image due to field rotation, constant shifts in images due to local variations in refraction (air turbulence) and general shifts in image position on the sensor and the consequential distortions (in particular when you apply fixed tripod techniques).

But you may generate a sensor- and scene-specific Camera Curve Profile Function (in PhtoImpact called CCF-files) while you produce an HDR image and such a CCF can actually be used to amplify the nuances of levels in single exposures. Over the years I have established a small library of such profiles and in the initial image on this page and in what follows I have used some profiles based upon series of images recorded when the moon was low in the sky and the differences in colour were thus, accordingly, the more pronounced. There is no exact science in this: One has to try out different profiles on each occasion, and the aforementioned "opening image" is probably "too tough a diet" for most. But here comes a more "normal" example:

1.  Stack a number of individual exposures (here 6) in Registax:




2. 
Increase sharpness and make a crude adjustment of levels (here in PhotoImpac) and make some, if so required, clean-ups of hot pixels, chromatic aberration, etc.:



3.a.  From hereon
you may then proceed with sharpening and contrast adjustments etc.:




3.b.  
But one may also try to find a suitable camera Curve Profile in one’s "library" and THEN you can get something like this ....




.... and that was merely what I wanted to show.

 

All images shown here are based upon the same 6 single exposures taken with an Olympus C-50Z 5 MP camera through a Tamron 350 mm catadioptric mirror tele lens with a 20 mm eyepiece, (Tamron SP 350mm f/5.6, Model 06B + Tamron TeleView wide-field adapter). The general set-up is shown here. The resulting focal length is 400 mm and the effective aperture is about f/6. All pictures were taken at 1 / 50 second at ISO 80. The pictures shown are full, un-cropped images. All images shown on this page are scaled down here from 2560 pixels’ width to 1100 pixels - which of course unfortunately does degrade the image resolution actually achieved in the originals.

 

One final note: You do not strictly need to apply those CCF’s / profiles. In principle you may achieve the same results by playing around with curves and levels, but THAT would be hard work to get reasonably right from time to time.

 

 

 

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