Milky Way Nightscape with the San Juan Mtns of Colorado


Posted by rnclark on Tue Aug 12, 2014 11:56 pm

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Summer Milky Way outside of Ridgway, Colorado

This scene is all natural light. The light on the land is that from the night sky: light from stars, the Milky Way galaxy, and airglow: light from molecules in Earth's upper atmosphere excited by solar ultraviolet light during the day and from cosmic rays. The molecules emit light throughout the night. The red is typically from hydroxyl (OH) 80 to 90 km high.  Green is from oxygen emitting at 557.7 nm.

Canon 6D digital camera, Sigma 35 mm f/1.4 lens at f/1.4. Thirty one exposures at ISO 1600 were made for the mosaic. On the sky, the camera tracked the stars using an Ioptron, with 19 exposures, 30 seconds each, then 12 images with 120-second exposures of the land were made with no tracking, with ISO 1600. On the land, 4 views were images and three 120-second exposures were averaged in each pointing, thus the four images of the land had 6 minutes of exposure each. The full sized image is 8129 pixels high by 7848 pixels wide (64 megapixels). 

More info at
http://www.clarkvision.com/galleries/ga ... n8x8s.html

Roger

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by crw816 on Wed Aug 13, 2014 8:02 am
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WOW! Look at that sky! Amazing process you went through to make this image. I suggest toning down the red just a little.
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by rnclark on Wed Aug 13, 2014 8:53 am
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The red is from emission lines at 630 nm (oxygen) at around 200 km high and 650-700 nm about 90 km high, so quite saturated red.

Roger
 

by E.J. Peiker on Wed Aug 13, 2014 9:46 am
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Absolutely love it but for my eyes I would like to see it with a lower white balance temp setting from an aesthetics point of view
 

by CactusD on Wed Aug 13, 2014 10:23 am
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This is awesome - the technical know-how and attention to detail required to make a shot like this work are very inspiring.

It certainly doesn't hurt to have a few versions of a shot with slightly differing colour balance; only you were there and know exactly what it looked like, but verisimilitude isn't the only goal I suppose.
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by Peter Ireland on Wed Aug 13, 2014 1:38 pm
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Impressive capture!
 

by rnclark on Wed Aug 13, 2014 6:12 pm
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E.J. Peiker wrote:Absolutely love it but for my eyes I would like to see it with a lower white balance temp setting from an aesthetics point of view
E.J.
I'm not sure what you mean by an aesthetics point of view.  I understand the prevailing view among digital photographers these days is a blue sky.  But the night moonless dark sky away from ciries is not blue.  The red and green airglow in the image is more muted than we see in aurora photographs but the emitting wavelengths are exactly the same with the same molecules emitting.

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by John Labrenz on Thu Aug 14, 2014 12:50 am
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Absolutely amazing.
Kudos on the technical ability to create this image....and thx for sharing the tech details.
 

by crw816 on Thu Aug 14, 2014 7:48 am
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rnclark wrote:The red is from emission lines at 630 nm (oxygen) at around 200 km high and 650-700 nm about 90 km high, so quite saturated red.

Roger
Hi Roger.  I read that, but still suggest a WB tweak at least for the green foothills.  They look very un-natural bathed in red despite the fidelity you have preserved with processing.  Don't get me wrong, its a great image, but to my eyes something just doesn't look right.  Perhaps that is because of the long exposures.  My eyes never perceive a night scene that looks quite like this, and perhaps that is due to the additional light collection from long exposures.  I won't dispute the technical aspects of the atmosphere or how the camera interprets them, I am simply critiquing based on my observation and preference.  
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by rnclark on Thu Aug 14, 2014 9:15 am
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Chris,

If we colored night images as we perceive them, we would make them largely gray. But think about the light. The light in this image from airglow is strongly red and green. The green wavelength, 558 nm, appears like a chartreuse green. The reds, 630 and 650-700 nm are deep red. Look at some aurora photos made way up north (or south) when the green auroral bands illuminate the landscape with bright enough green that we can see the color. It is an unusual color. Do you change the color balance of your auroral images to make everything blue? At a sunset with alpenglow, do you correct the mountain top to be rock brown? When a red sunset is illuminating snow on a mountain, do you change the color balance to make the snow white? While the reflectance of clean fine-grained snow is white, when illuminated by a strongly red sunset, it shows as red.

In the case of the posted image, the green band is low on the horizon and the red above it. Both red and green are illuminating the fields in the foreground with narrow band light, making for intense colors. The snow on the mountains is north facing (the view looks south), so the snow facing the camera was not illuminated by the green band, but was from the red higher up, so the snow only appears red.

An analogy to the current fad of the night sky is blue, a completely false reality, is if photographers decided sunsets are blue, and all sunsets, no matter how red, were changed to blue. The reality is the night sky is full of wonderful colors, and upper atmospheric phenomenon add another dimension in the waves of colors that are constantly changing. When one changes the color balance to everything is blue at night, these wonderful and varied colors are suppressed.

Here is my article on the color of the night sky (though I will be doing a major update to it, especially the film section):
http://www.clarkvision.com/articles/col ... night.sky/

Roger
 

by crw816 on Thu Aug 14, 2014 9:26 am
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You can take my critique or leave it. As I previously stated, I'm not going to debate with you. My comments are strictly directed towards the image as you presented it and in my opinion, it could be improved. Ultimately, what I think is irrelevant, as it is your image, so do whatever you want... Just keep in mind that when you post your work to a image critique forum, that you may receive feedback or opinions that differ from your own and with this in mind the science is irrelevant.
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by Kim on Thu Aug 14, 2014 6:11 pm
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It is what it is and I for one accept it as presented. It looks fitting as a slice of the universe and something my primeval brain seems to intuit on solitary camping trips at night in the wilderness.

One thing I do not understand Roger in your comments though is the 'artificial' blue night sky. I for one have taken a series of images after sunset in what is known as the blue hour for a client of their commercial outlets, McDonalds here in Australia, to get the 'blue sky' as requested by the client. I did nothing to the RAW files other than standard work flow to get the skies blue the files where like that. So is there really no 'blue hour' and if so how is it that the files were like that on download?
 

by rnclark on Thu Aug 14, 2014 10:57 pm
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Kim,
Certainly twilight is blue, and in fact bluer than the daytime sky. But as twilight fades as the sun drops below the horizon further, the blue goes away (a little over an hour at low latitudes, around 2 hours in summer at mid latitudes, and longer for polar latitudes), sunlight is simply not there to be scattered (Rayleigh scattering) and the blue goes away. I've added a new section on the twilight blue (and twilight green) on my color of the night sky article:
http://www.clarkvision.com/articles/col ... night.sky/

Chris,
I do appreciate the critique. I acknowledge that the prevailing view of night images is to make them blue, and I expected some push on that side when I posted the image. But I'm trying to show the colors that are really there. So we can differ on that aspect. Some like the everything is blue for the mood, with the night cold. To me the night is warm and inviting. I like to show that aspect.

Roger
 

by Kim on Fri Aug 15, 2014 12:48 am
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Thank you Roger, I read it and understood it.
 

by Missy Mandel on Fri Aug 15, 2014 7:27 am
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This image is absolutely beautiful. Congrats on EP!
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by Wade Thorson on Fri Aug 15, 2014 5:16 pm
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Really cool. I do think it looks Mars-ish, and find myself in the wish it were cooler camp. The beauty about night photography is there really is no basis for comparison to reality, because the eye cannot see what the camera does...
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by rnclark on Fri Aug 15, 2014 5:53 pm
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Wade Thorson wrote:Really cool.  I do think it looks Mars-ish, and find myself in the wish it were cooler camp. The beauty about night photography is there really is no basis for comparison to reality, because the eye cannot see what the camera does...
Thanks all who have commented.

Certainly what you say has some truth, but one really does see some colors.  For example, the bright stars, do show colors with the unaided eye.  Antares (the bright star near the right edge in the image) is distinctly orange to the (normal) eye.  Altair (upper left corner) is white/blueish-white.  If really well dark adapted (no bright red lights) the star clouds of the Milky Way around Saggittarius shows a faint brownish color.  If you use a good telescope, some of the red emission nebulae do appear a pastel pink (M8, M20 in the image), and blue reflection nebulae do appear light blue (M20 northern component).

The airglow also shows color when it gets bright enough.  On the night of the posted image, the green band on the horizon did have a distinctly greenish-gray color compared to the sky above (the red was to faint to distinguish color).  As the airglow brightens, the color comes out, and I have seen pinks, greens and reds many times over the last year or so from Colorado.

The digital camera is bringing those colors out much better of course, but we can typically verify that the hues are correct based on those colors we can detect, especially the colors of stars.

One key factor in seeing color is to be well dark adapted.  I rarely turn on a light.  I usually work only by star light, except for the LCD light on the camera (which blows away my night vision for several minutes).  I see many photographers using bright red lights.  That destroys night vision and warps color perception.  If you've been exposed to red light and you then look at something dark, it appears blue.

Roger
 

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