Make and Edit Pictures of the Milky Way

Lonely Speck

Photographing the Milky Way was the motivation for me to finally get deeper into the art of photography. In preparation for a trip to Albuquerque, New Mexico, I had already bought a new camera. The next step was to learn how to make the best use of my equipment – and in particular, how to get the best out of the pictures afterwards, at home on my computer. What helped me the most in all of this was the YouTube channel “Lonely Speck” by Ian Norman, which I will introduce here.

Milky Way over New Mexico
Milky Way over New Mexico

PREPARATION

PLANNING

I spent about a week in Albuquerque, including a few open evenings. While looking for tips where and how to best see the Milky Way, I came across Astronomy Adventures. Peter has a dark site on a ranch up in the mountains between Albuquerque and Santa Fe, at about 7,800 ft. elevation, where he offers guided tours through the night sky with his telescope. Together with a couple of friends, we had the great luck to catch a clear night at new moon – perfect conditions. Peter’s explanations of the history of astronomy, while pointing out interesting stellar formations with his telescope, made for an unforgettable experience.

Back home, in a densely populated region such as Germany’s Rhein-Main area, catching a view of the Milky Way is not so easy. In order to see a decent amount of stars around here, one would have to go to the northern Black Forest, or to the coast of the Baltic Sea. The web site www.lightpollutionmap.info provides a very detailed overview on light pollution levels; check it out for dark places near where you live.

Full Moon Rising
Full Moon Rising

A natural form of light pollution is the moon. In a full moon night, there isn’t much else to see in the sky. There is a number of web sites and apps that help you out with what phase to moon is in, or when it and the sun set and rise respectively. A good recommendation is The Photograhper’s Ephemeris, which can be used for free on any desktop computer. Then of course the weather has to be right as well – the fewer clouds, the less humid and the colder it is, the better. And last but not least, the Milky Way or whatever constellation you are interested it, has to be visible on the sky. There are plenty of web site and apps for this as well; personally, I use Sky Guide for iOS.

EQUIPMENT

This topic can be quickly summarized. You’ll need:

  • A camera (the bigger the sensor, the better – however, even with a Micro Four Thirds camera you can take great pictures. With your cell phone… not so much)
  • A lens. That should fulfil the following requirements:
    • Widest possible angle, to capture much of the sky
    • Widest possible aperture (i.e., low aperture number, so that as much light as possible reaches the sensor)
    • For APS-C DSLRs, I recommend the Tokina 11-20mm ƒ/2.8 DX, which is what I am using
    • For other camera systems, I gladly pass on Stephan Wiesner’s recommendations: for mirrorless APS-C cameras, the Samyang 12mm ƒ/2.0; and for full-frame cameras, the Tamron 15-30mm ƒ/2.8.
    • However, expensive gear isn’t mandatory: even with your kit lens you can take great pictures, as will be shown below
  • Sturdy tripod
  • Optional: remote shutter release (if you don’t have one, you can use your camera’ two second delay shutter)

In addition: warm clothing (even in summer, clear nights tend to get cold), food, drinks, and a book. Also quite helpful: a flash light with a “night vision mode” (red lamp), so you can check or search something without blinding you or others in the dark.

TAKING PICTURES

Once everything is in place, line up your camera with the section of sky you’re interested in, and off you go. The most challenging feat is focusing correctly. In the dark, you have to focus manually, and simply turning the lens to “infinity” rarely does the trick. I usually look for a star that is bright enough to appear in Live View on the LCD screen, use the 10x magnification on it, and turn the focus ring until the star appears as small as possible. I take a few test shots in addition, zoom in, and then fine-tune as needed until the stars have become tiny pinpoints.

I typically start out with these settings:  11mm | ƒ/2.8 | ISO 1.600 | 25 Sec.

If you do not want to capture star trails on purpose, you cannot keep the shutter open for as long as you want – the earth rotates faster than you might think. Here is a rule of thumb for the maximum exposure time so that the stars still appear as dots: (500 divided by (focal length * crop factor)). The crop factor defined the relative size of your camera’s sensor compared to a full-frame camera. It needs to be taken into account because smaller cameras usually also have smaller pixels, hence are more sensitive to the movement of the stars. For a Canon APS-C camera like mine, the crop factor is 1.6 (it’s 1.5 for Nikon, and 2 for Micro Four-Thirds). So, with my camera and the Tokina 11-20mm, I can keep the shutter open for a maximum of (500 / (11* 1.6)) = 28.4 (rounded down: 25) seconds. Please keep in mind: this is a rule of thumbs. Check your images; you may find that you can keep your shutter open longer, or not as long, to get the desired results.

Always shoot wide open, to gather as much light as possible. Concerning the ISO setting, I usually start at 1,600. At least for my 760D, that is a good compromise between the amount of light gathered and the image quality. Once you’re all set, start taking pictures. And never take only one image of a particular target area; always take a series of pictures. I usually take 16 frames or more. This does take a while, but it drastically increases your post-processing options afterwards.

Milky Way and Andromeda Galaxy
Milky Way and Andromeda Galaxy

In closing, there is one important point to consider: when doing night sky photography for the first time, you’ll get easily tempted to make the pictures too dark. They’ll look great when you look at them on your camera’s bright LCD screen in the dark of night, but back home at your computer, you’ll be greatly disappointed. Make the pictures so that they actually look too bright at first! If your camera offers a histogram, use it. Of course, no parts of the pictures should be blown out (completely white), but there definitely should be information on the right hand side (lights) of your histogram. The more light there is in the image, the more information is available for post-processing – which brings us to the actual topic.

POST-PROCESSING

Ian Norman is a photographer living in California who specializes in astrophotography. Consequently, his YouTube-Channel offers a lot of information on this topic; in particular on post-processing the images. His tutorials explain the steps to be taken in Adobe Lightroom and Photoshop very well and in an easy to follow manner. When I edited my first night sky images, I always had my iPad running the video tutorial at hand. I paused, scrolled back and forth, and followed each step carefully. By now, I can do most of it without having to ‘cheat’.

EDIT SINGLE IMAGES IN LIGHTROOM

The big challenge is in achieving good contrast and bringing out all the details, so that the image still looks natural and not overloaded. You will notice that the camera sees a lot more stars than the naked eye does. However when manipulating the night sky, and in particular the colors in the Milky Way, there always is some artistic leeway of course.

I want to point out two of Ian’s videos in particular. In the first one, he explains how you can capture the Milky Way even under very difficult lighting conditions:

This also explains very well why it is better to make the images appear too bright in camera and then reduce brightness in post, than the other way around.

The second video walks you through the usual editing steps for night sky images in Adobe Lightroom. This also proves that you can take impressive pictures even with a slower lens, if you take some considerations into account:

Both videos describe the editing of single images. The advanced method is to merge several frames in Photoshop into a single image – but for this, the images are initially edited in Lightroom as well, before bringing them into Photoshop.

MERGING SEVERAL IMAGES IN PHOTOSHOP

Due to the physical limitations imposed on aperture and shutter time, it is inevitable to raise the ISO setting to 1,600 or even 3,200 when taking pictures of the night sky. This results in a visible amount of noise in the image, especially when zooming in. Using the default noise reduction algorithms included in most photo editing tools will result in losing a lot of details, such as smaller stars.

Now it comes in handy if you have taken several shots of the same area of the sky. The more, the merrier. In short, the trick is to stack and exactly align the images, and then to compute the average value for each pixel. As the stars will always be in the same places in all images after correct alignment, they are not affected. The image noise, however, is random and thus cancels out when calculating the median. If you combine four images taken at ISO 3,200 this way, the remaining noise will be comparable to a shot taken at ISO 800. For the Milky Way pictures you can see in this post, I have stacked more than 20 images each.

This video offers the detailed instructions for how to achieve this:

The particular challenge is the correct alignment of the images. If that does not match exactly, not only the image noise will vanish when calculating the media, but the stars as well, at least in parts of the image. As long as the pictures offer enough contrast, Photoshop’s auto-alignment will work very well. However, I had a number of occasions where the automatic alignment failed. This is no reason for despair, though, as there is a manual workaround:

What remains is the artistic design of the night sky. Ian explains how to best bring out the colors and details in the sky in this video:

This works not only for Orion, of course, but for every section of the sky that has to offer similar features.

Ian’s channel offers numerous other tutorials as well, which are all very helpful. If you have taken enough shots of a particular area, you might for instance consider turning them into a time-lapse video. Using the knowledge from these videos, I have taken quite a number of pictures of the night sky so far, and I am increasingly happy with the results. As with all other kinds of photography, practice makes perfect. So, then: wait for the next clear night around a new moon, and then take your camera out! Especially now during the long winter nights with their clear, cold air, the conditions are ideal…


CONCLUSION

Recommendation: Absolutely watch, then go out and try!

What I’ve learned: The knowledge what to consider when taking the pictures, and how to post-process them, is a lot more important than the equipment. Thorough preparation is important, as well as the necessary patience while capturing the images. The results in the end will be well worth the effort!


LINKS

FURTHER INFORMATION

Picture credits: Title image: YouTube Screenshot; Milky Way and Moonrise: own images

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