Advanced Star Trail Tricks

Published: Oct 11, 2012
Last Update: May 2, 2021 (remove obsolete)

I have been playing with Star Trail processing for quite a while.  Ever since I wrote the StarCircleAcademy Stacking Action I’ve been tweaking processing to try different things. Sometimes failure is inevitable, sometimes… well, you’ll see.

First, you may want to look back through my earlier columns on shooting and processing star trails because this is not a primer on star trails – it builds on what I’ve previously written and this is not a good place to try to understand what stacking is.

Second, please understand that I use a variety of tools but almost all of my more successful endeavors end up as layers that are combined in Photoshop (CS5 at the moment).  You could combine your layers in GIMP if you don’t have Photoshop, but you’ll be out of luck if you try to use Lightroom.

Here are my star trail effects:

  1. Smoothee – Averaged sky and/or foreground to reduce the grittiness that sometimes results from brighten stacks. I’ve been espousing this for quite a while. See the Simple Astrophotography Processing Technique.
  2. Blobulous – stars at the beginning (or end) of a trail are made to stand out from the rest of the trail.
  3. Comets – star trails appear to grow brighter and the end of the trail looks like the nucleus of a comet.
  4. Streakers – Like comet only the trails are longer
  5. Blackened – A clever trick removes sky glow from light pollution, the moon, or twilight.

And of course you can make “Blobulous Comets” and “Blobulous Streakers” and “Blackened Smoothee Comets” and more.

Building Blocks

To creatively combine exposures, I usually create the following stacked frames.

  • Dark (Darken in Image Stacker/StarStax)
    The darkest elements emerge – especially the hot pixels
  • Brighten (aka lighten) stack
    The Brightest of everything is present, including hot pixel and more noticeable noise
  • Average
    Contrast is reduced, smoothness increased.
  • Additive (called “Stack” in Image Stacker)
    Hot pixels become really bright.
  • Scaled (called Stack/Average in Image Stacker)
    Allows some increase in brightness but more smoothness, too. Experiment with different divisors.

Normally I create all of these combinations using Image Stacker against my JPG files because it is really easy to do.  I end up with a set of frames something like these although I’ve significantly brightened them so that they are easier to see.


In a Nutshell: Combine the Average stack over the Brighten stack using Normal mode at 45% opacity.

I’ll start with the Smoothee technique since it’s probably the easiest to do and perhaps the easiest to understand.  The problem with “Brightness” (or lighten as it’s called in Photoshop) is that it will also pick up all the hot pixels, and the brightest bits of noise.  Averaging on the other hand tends to smooth out everything except for truly hot pixels since most noise is random. By putting an averaged stack as a layer over the brighten stack and then adjusting the blending modes and opacity you get a smoother sky and foreground.  Exactly what settings to use depend on the images, but surprisingly many of the blending modes for the Average layer work here including Darken, Multiply, Overlay, and Normal. The starting place for Opacity is about 45%.

Hint: You can also use an Additive stack instead of the average stack but usually only the Normal blend mode will work.  For even more fun combine the Additive stack and the Average stack.

For additional smoothness you can also subtract the “Darken Stack” while adjusting the opacity to prevent halos and weirdness.


In a Nutshell: Add one of the single frames more than once.

What do “Blobs” look like? Like this…

“Fat Star” processing.

There are two ways to produce “Blobs”. One way is to add “Comets” to a smoothed star trail. The other is to simply pick an image (usually the last one in the set) and add it in using “Add” or “Screen” mode. To make the blob more pronounced duplicate the last frame so it’s added twice. BUT remember when you add in any single image the hot pixels are going to come out… and even more so if you add an image twice.

Comets and Streakers

These two techniques require some fancy stacking techniques. Fortunately I’ve created an action to do all the fancy stuff – but it has been withdrawn from sale because it became too tedious to keep it up to date (especially on a Mac).

Oh, here is a peak at what the Comet action looks like:

What's The Point?

And here is what an animation of comets might look like:

Star Rise


I know you’re going to ask so let me save you some typing. Except for the “Comet” image above, all images used in these illustrations were taken during the Ancient Bristlecone Pine Workshop in the Patriarch Grove on White Mountain, East of Bishop, California.

The 34 or so images that I’ve combined in the examples above were all taken with the following settings: Canon 50D, ISO 400, f/3.5, 79 seconds, 10-22mm lens at 15mm.

8 thoughts on “Advanced Star Trail Tricks

  1. Tom Piekunka

    Hi Steve,
    I am very interested in knowing how you produced the “comet” effect above. I see the exposure is 79 seconds, so that set the star trail length, but how did you produce the “effect”? I would definitely welcome the opportunity to be part of your test cadre for the action you developed. I am waiting for the email to finalize my registration so I can participate in your web seminars.
    Tom Piekunka

  2. Tom Piekunka

    Hi Again Steve,
    In Brad Goldpaint’s fantastic timelapse video “Within Two Worlds”, he has a sequence where the night sky is filled with stars and then trails accumulate to form the many streaks and circles of a time lapse image. He also has a sequence over Mono Lake where it starts with stars in the sky and then time lapse streaks extend and then catch back up with themselves back to the night sky with stars. If you have the opportunity, I would love to learn how to produce these cool effects. He also has a star comet sequence over Raibow Falls on the John Muir Trail in the Sierras.
    Thanks again,
    Tom Piekunka

  3. Graham Wiffen

    These effects are great for single images, but can they be applied for Time Lapse sequences?
    I usually do my TL sequences in LR, which doesn’t have the flexibility of PS …. you BrownSky tutorial cant be done in LR as far as I can tell.
    Does this mean that all TL images have to be put through a PS action first to make them look better, before turning them into the TL sequence? or am I missing something?
    Thanks Graham

    1. Steven Christenson

      I added a timelapse video created using the Advanced Stacking Action, above. It uses the comet technique.

      Your statement “Does this mean that all TL images…” is really broad. It depends on the effect you want, of course. Editing things in Photoshop is not the only way, some timelapse creation methods can do their own “tricks”.

      Lightroom is very limited in what you can do. You can do parametric edits to single images, apply those edits to multiple images, but Lightroom does not do layering, HDR, nor much of anything else natively. Indeed much of what you might want to do with LR in the way of image manipulation you can find in simplified form in Adobe Camera Raw or ACR + Bridge. If you’re Lightroom constrained, I’d say the answer is yes, you must edit images. If you’re not Lightroom constrained (using say plugins, or external tools like Photoshop, Elements, and more) then more is possible. Applying a “brown removal” level to multiple images is relatively easy with Photoshop actions. Some clever LR person might be able to accomplish something similar in LR but I’m not sure.

      I have had a “super advanced” stacking action” on the back burner for a while. It ups the ante, but relies, not surprisingly, on Photoshop’s raw power.

  4. Pingback: Photographing Stars at Monument Valley | Kit Frost

  5. Johan Sisno

    just trying out strartrails and night photography. i live in the philippines so the foregrounds here are quite different. thank you for your website for the guidance:)


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