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Astrophotography Part 2: Getting More Out of Your Images
By Zac Henderson

This is the 2nd post in our series on astrophotography. In the first post we discussed the basics of photographing the Milky Way and how to get some properly respectable images of the night sky in a singe image. If you haven’t already read it, here’s a link. Go ahead, we’ll wait.

Ok, now that you’ve read the first post in this series we’ll talk about getting more out of your images of the Milky Way and some more advanced techniques employable during capture to gather more information for the best image possible.

Like we discussed in the first post, sometimes it can be a good decision to capture some foreground interest in your image of the night sky to turn the image into a landscape. This has the effect of providing depth and perspective to the image. This is a good choice, however because the night sky is so dark there’s likely little light hitting your foreground. A fully blocked up foreground silhouetted against the night sky can be done purposefully and, depending on the silhouette, can be quite pleasing. However, if you’d like to capture information in your foreground you’ll run into issues.


For starters, as we discussed in the first post, the stars and your foreground element are quite far from each other. This has the effect of forcing you to choose between focusing on the foreground or the background. Should you choose to focus on the stars, your foreground will lose detail. Combined with the increased noise inherent in underexposed images, you’ll likely end up with a very muddy foreground. Should you choose to focus on the foreground, your stars may cease to be points of light and may appear as ill-defined, messy, and distracting.

The fix here is to expose two separate images: one for the foreground and another image of the stars in the background to be later combined in Photoshop. The benefit to this technique is two fold by allowing you to both expose and focus properly for stars as well as your foreground separately.

CompositeTo make the background exposure of the stars you’d likely follow the standard methodology we mentioned in the first post of the series, although we’ll discuss other options shortly. For your foreground, you have more options. Because you’re exposing separately, your shutter speed is much less critical of a consideration. Since you have an exposure dedicated to the sky already, it doesn’t matter how much the stars trail in your image of the foreground. You’ll be combining them both in post in any case, so you’re looking for as much information as you can reasonable gather of that cool tree in front of you.

The keyword there is reasonable. Remember, you’re photographing the night sky. Usually things are pretty dark at night, so if your foreground looks like it’s been exposed during the midday sun you might end up with a very unrealistic looking image which may or may not be your end goal. Combining these images in post in Photoshop requires a refined hand for a realistic image. You’ll likely want to keep your foreground dark, but leave information still readable by the viewer.

Another option for gathering more information for your foreground is to light your foreground artificially. This involves using artificial light sources like flashlights or ice lights to shine light on specific parts of the image you want the viewer to pay most attention to. Obviously strobes will work, however continuous lights like LEDs allow you to paint with light and offer more versatility. A good option from our stable is the Genaray Beacon LED Wand Light. Include the light source within the frame for some truly interesting photographs. This option has become increasingly popular with nighttime photographers and unlocks untold amount of creative potential.

Light Painting

As mentioned above, you have options for photographing your foreground, but you also have more options than you might think when photographing the stars. Once you’ve made the decision to composite two separate images together so you have more control over your foreground, its not so far of a stretch to start considering similar techniques for capturing more detail in the sky.

One such method is to employ the use of a star tracker. These handy gadgets will counteract the rotation of the earth by rotating at the same rate, but in the opposite direction. With a star tracker you you have the ability to expose for several minutes rather than just a few seconds, and without any blur. This is a huge benefit for capturing stars since you can reduce your ISO sensitivity, and in doing so reduce noise, while also exposing for a long enough period of time to “expose to the right”. That is, slightly overexposing your image so that you can bring the exposure down in a RAW converter instead of being stuck with an underexposed image and boosting the exposure (and noise) in post. Using a star tracker also renders stars as much finer points of light, and due to the long exposure times possible, can bring out extremely faint stars you may not have even seen with a single exposure.

Star Tracker Comparison

On the left, a 5 minute exposure at ISO 800 "exposed to the right". Opposite, a non-tracked image shot at ISO 3200 at 25s with a more or less "locked" exposure. Increasing exposure further in post or in camera would introduce more noise.

Of course the downside to the star tracker is added complexity. Before each use star trackers must be aligned with the northern star Polaris (if you’re in the northern hemisphere). Depending on the focal length of the lens you’re using, this could take a few seconds or several minutes. Again, should you choose this method to photograph the stars but prefer to put some foreground interest in your images, you’ll need to add a second exposure of the foreground since any movement from the star tracker will blur any detail in the foreground.

Star Tracker

Lastly, there is the image stacking method of capturing stars. This method is unique in that it takes several exposures of the same subject and combines them via highly complex pieces of software.  A few options are PixInsight, Nebulosity, and Deep Sky Stacker (Windows only).

The idea here is to boost “signal” and reduce “noise”. The stars in this case are the signal. They are static across multiple images (either via a tracker or aligned in post), while noise by definition is random. Software understands this and by averaging the exposures together through some complex math, the final image will keep the signal and greatly reduce noise. Images taken with a star tracker as well as averaged together as mentioned above are referred to as “tracked and stacked” by the astrophotography community, and tends to be thought of as the gold standard for the highest level of detail possible when photographing the night sky, but naturally also requires the greatest level of planning and forethought, not to mention the extra gear and software.

As you may be able to gather, photographing the milky way can be as simple or as complex as you like. The key is to experiment and have fun. The Milky Way is a wonderful subject and a joy to photograph, not just because of the unique final images possible, but also because of its significance. Standing in the dark with nothing around you but the night sky is a good time to consider the weight of the object you’re imaging. Our galaxy. In a sea of other galaxies. Our home in the universe. The core of which is a place where space and time literally bend themselves into oblivion amongst gargantuan explosions millions or billions of years old forging the very life giving materials we’re made from. When you’re photographing the night sky you’re capturing photons that have travelled billions of miles through millions of years to be focused by your lens and registered on your camera’s sensor. Thats a pretty cool subject to take pictures of if you ask us.

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