You may have noticed browsing on Internet that there are many photographs of the milky way, often different from each other and with many imaginative colours, which one is the correct one?
To try to do a bit of clarity, it must be said that regardless of which use a camera modified for astronomy or not (more sensitive to infrared) the milky way does not change colour and with a good processing, and different lens / astrographs, will always produce the same hues, as well as for deep sky objects, to any focal length you take pictures, the correct colors are about the same and over the entire filmed you will see stars of various sizes and coloring, one yellow and one blue.
There may be a component of the gradients generated in photos from nearby light sources, light pollution, which plays tricks to the inexperienced photographer and is probably one of the reasons for misleading so we see on the images on the internet so many different shades of the milky way.
Another cause is definitely the color balance in the camera, which if ignored when shooting, it cannot be ignored even in preparation of the shots, and of course the creative component in each of us 🙂
To make an example of color balance, with any graphics software you can see the current histogram of the picture and modify it, even on a generic program like Adobe Lightroom! The first proposed image is “unbalanced” as it could be the shot in the rough, note the histogram in the top-right corner, also with RGB colors not aligned, with a prevalence of red/yellow
Now by pressing Temp (colour temperature) and Tint (hue) you can calibrate the image and get a good calibration as in the second image, the histogram now has the three RGB channels more aligned
The photograph was taken at around 4 a.m., almost matching colors, from green meadow below the light orange red incadescenza led to the caravan of the telescope, and find your accommodation we can distinguish at last the stars, blue and yellow.
Then you have to immediately clarify that one thing is take 1 single Nightshots the milky way by 20 seconds, whose quality and color rendition is due mainly to good color calibration and especially cannot stand trial heavy processing, because it has too little signal would be outside more “noise” that signal itself!
In fact, it is one thing to process a single shot, another thing is to draw up a sequence of shots and then loaded on the computer literally “stacking” or do the stacking, to get a single image that contains all the individual pictures taken and related minutes of exposure, and then signal.
A trick that I reveal is definitely a good dark sky where rises the milky way, because more light pollution is present on the site chosen for your photography you will present themselves in the shots gradients unwanted and becomes prohibitive to take on the area of the horizon from where the light sources.
Finally some examples of wide field milky way pictures:
with an unmodified DSLR, fail some shades that match the infrared cut band, the colors are more mild, but it’s still possible to “balance the image in RGB” because the colours retain approximately the same color cast.
While with a DSLR last for astronomy has a variety of colors and intensities, and anyway the photo is made with a focal lens 100 mm or 24 mm, or 10 mm ultrawide, colors will always be the same, provided that the same area framed, try it:
Brighter colors or not, the important thing is to definitely avoid saturation boost that blinded some areas in which the details are less, to effect similar to overexpose, burning parts of the photo, and it is also right that limit the saturation, as long as it is not penalized the image so as not to intensify the noise with the saturation is accentuated as to details.
It takes both good taste and common sense, knowing how to push the image until it becomes unpleasant and from the point of pure beauty and inaccurate, unlikely, surreal, even from the point of view of ethics and science.
Latest information and photography, we have so far posed shots of the area of the milky way South, above the horizon (for us who live in the northern hemisphere) that typically has a yellow color, while at the same time you take over your head (the zenith) we will have other constellations and other portions of the milky way, where the predominant color is blue and red due to the presence of many emission nebulae in the area.
That’s all for now, I refer you to our first set of Video Tutorials on how to develop your first shot!
clear skies! ♣