Photographing star trails involves a lot of complications. In this video I go through the entire process of photographing the star trail including dealing with light pollution. Then I go through an entire edit from start to finish. I edit the RAW files in Capture One, and then iterate through stacking the images in StarStax and removing airplanes and clouds in Affinity Photo.
Photographing Star Trails the Simple Way
Things kick off with photographing a star trail the simple way: using a “dumb remote”. This method works with almost any camera system and requires only a super cheap wired remote. Set your camera for a 30 second exposure, and continuous-high release mode. To take the star trail, lock the button on the remote “on”. The camera will take 30 second exposures as fast as possible.
For more information on this technique, check out A Star Trail Photography Primer. For information about the different types of remote releases available, see my remote release article.
Editing a Star Trail: Capture One, StarStaX and Affinity Photo
There are a lot of complications that can arise when shooting a star trail. Light pollution, airplanes, moon rise, and clouds are just a few of them.
When I edit a star trail I take an iterative approach. I start by processing one of the images in Capture One. Once I’m happy with an individual image, I sync those adjustments to all the images in the star trail and export the resulting images.
StarStaX <-> Affinity Photo
Once the images are exported from Capture One, I open them in StarStaX and do a quick lighten-only stack to see where things stand.
In a location like this, facing Los Angeles, airplanes are a serious issue. I use two different strategies for removing airplanes from my star trails. Which strategy I use depends on how the airplanes are moving relative to the stars. If their movement is close to parallel to the stars (as they are in this star trail), I will remove them from the individual frames. If they are moving perpendicular to the star trails, I will remove them from the finished star trail all at one time.
Once I go through all the images once removing all the planes I see, I return to StarStaX and restack them. Normally, as I did this time, I missed some planes and I have to make another pass or two through the images removing unwanted plane trails.
Once I’ve got all the defects removed, I switch to “Gap Filling” mode in StarStaX. Gap Filling is fundamentally based on Lighten Only blending, but is much slower. I wait until my final pass to use it as a way to speed things up.
Blacking Out Defects
To stack a star trail, we keep only the lighter pixels from each frame. Because of that, I can use a black paint brush to remove areas of individual frames. The blacked out areas will be overwritten by the other frames in the star trail.
There are two advantages of this method over something more complicated, such as the InPaint brush. First, it is faster. The computer doesn’t have to use a bunch of complex AI to fill in the area. Second, no fake stars are added in the cleared area. InPaint doesn’t know where stars should be and sees them as texture. It will often duplicate nearby stars adding a new defect and breaking up your star trail.
The disadvantage of blacking out defects is that it can create breaks in individual star tracks. This isn’t a big deal for me most of the time as long as there are enough stars in the sky. A viewer won’t notice the breaks unless they study the image closely searching for them.
The same approach works on clouds that wonder through the frame. In this star trail, the combination of light pollution from the city and the moon lit up some clouds in the center of the frame. The lighten only blending would keep these clouds since they are brighter than the background. Rather than throw out entire frames, I simply black out the clouds.
Final Retouch in Affinity Photo & Capture One
With the final “good” version of the star trail stacked up, there are normally some other defects I have still missed. I make a final pass over the entire image in Affinity removing any planes I missed. Then I reimport the finished JPG back into my Capture One project catalog and make any final tweaks needed, such as adjusting the black point.
Because lighten only stacking tends to brighten the entire frame (it keeps the brightest version of every pixel, even if it is only brighter due to noise), I normally pick a new black and white point using the Capture One levels tool.
The Finished Star Trail
I’m the first to admit this is not the most brilliant composition for a star trail, but I still like it. It was a best effort during a for-fun camping trip over the Christmas holiday. I like east or west facing star trails despite the conventional wisdom that says you should always face the pole (north). I was pleasantly surprised how well this came out given the light pollution, clouds, fog on the filter and nearly full moon. My Pure Night filter helped a lot with the light pollution.
Andrew is a photography instructor teaching students of all skill levels in Austin, TX through Precision Camera and independently in San Diego, CA. He runs workshops around the United States.
He is a self taught experiential learner who is addicted to the possibilities that new (to him) gear open up. He loves to share the things he has worked out. Andrew started with a passion for landscape and night photography and quickly branched out to work in just about every form of photography. He is an ex-software developer with extensive experience in the IT realm.
Andrew is a full time wedding and commercial photographer in both Austin and San Diego. Andrew is a club founder and multi-time past president of North Austin Pfotographic Society.
