Creating Star Trail Images (Part II)

It’s time for the second installment on shooting star trails. In Part II I explain how to take the group of images you captured in your camera (from Part I) and put them together into one complete image. Before we start, I would like to point out that while  this is the way I like to do this process, there are many methods out there and everyone has their own opinion on which works best. As I said earlier, you will need Photoshop CS5 and you will need to have your images in one folder on your computer desktop. Before I go any further, I’d like to state that this is a very technical article, and the technique explained requires some computer skills. I will try, however, to make it as basic as possible.

Loading the Action:

To begin, I need to teach you a little bit about a function we will be using in Photoshop called “actions.” If we were to do the process of creating a star trail by hand, we would need to click the very same buttons for all 400 of our images. With actions, we can have Photoshop apply those same changes to all our images for us…..AWESOME! An action is simply a little set of instructions that tells Photoshop what to do in a certain sequence of events.

We could build our own action, but a much easier way to go about this is to download one already made for this purpose. A very simple one that I have found is available here.

Once you get this action downloaded, you will need a place to put it. Photoshop really doesn’t care where this action lives, but if you plan on downloading different kinds of actions, you might want a place that you store all of them. To keep things simple, lets make a new folder in our “Documents” folder and store them there. I am going to call mine “My Photoshop Actions.” Once you have created that folder, simply drag the downloaded action into that folder for safe keeping.

So, let’s review what you should have right now. You should have a folder of star trail images (in JPEG) sitting on your desktop. If your images are in the RAW file format, you can run them through Photoshop or Lightroom to convert them to jpegs. You should also have a folder in your “Documents” folder that has your action that we just downloaded inside of it. Everyone up to speed?? Great.

Next we need to actually load that action into Photoshop. Open Photoshop and make sure that your “Actions” palette is opened. If it’s not, go Window —> Actions.

Next, click on the button in the upper right-hand corner of the Actions palette, choose “Load Actions…”  A browser window will pop up and you will need to go to your “Documents” folder, then find that action that we moved in there, hit the “Open” button. We have just loaded our action!

Running the Action:

We’re almost to the fun part!  First, we need to do a couple more steps before we can see the stars move before our eyes. In order for this to work, we will create a new document where the computer can place our star pictures. This blank image must be the same size as our original images that are in the folder on our desktop.

To determine the size of the images, take out a pencil (or pen) and a piece of paper (I know…..low tech) and open your first star image in Photoshop. We need to find the exact size of this image, go Image —> Image Size. Inside the Image Size dialog box, write down the pixel “Width”, “Height” and “Resolution”-  we will need this for later. Now close the image you just opened because you are done with it.

Next, go File —> New we need to create a new blank document to paste our star images onto. There is no need to name your new document at this point, but we must put our width, height and resolution setting into the box. Hit “OK” to create your new document. Now we need to fill this new blank document with black (the action only works with a black background). Go Edit —> Fill, where it says “Contents” choose “Black,” your new document should now be entirely black.

Now for the fun part!  Go File —> Automate —> Batch and in the top section of this box, choose the action that you just loaded into Photoshop (mine is called “Action 1”). Where it says “Source” hit the choose button and navigate to that folder of images sitting on your desktop. Leave “Destination” set to none. Hit “OK” and watch your computer do the work magically before your eyes.  After about an hour (on my computer) you should be left with a beautiful image of the night sky. You can now save that image or work on it a little more in Photoshop.

That’s all there is to it. Ok, I know that’s a lot of steps, but I have tried to provide you with enough detail to get you through it.  This might be a little hard if you are new to computers or Photoshop, in which case I encourage you to consider one our courses to help you become familiar. Anyway, I hope that this whole process goes smoothly for you!

5 thoughts on “Creating Star Trail Images (Part II)


Tried the manual way and ended up with this.

Opened all my raw files in CS5 and layered them using the lighten blend mode.

Trying your method now using the action.


My manual process was the same as Tom’s. Open images as layers, set blend mode to ‘lighten’ or ‘screen’ (depending on preferences) on the first one, copy that layer style, select all the other layers, and then paste the style into all of them.

I’m very curious if the ‘action’ method produces significantly different results, and if so, what it’s precisely doing.


Running it now. One thing. Be certain you don’t has CS5 set to open JPG file in ACR. If you do you’ll have to click ‘Done’ on ACR for each file. Mine started that way but I was able to change it in Bridge and it is continuing with out that annoyance.

Oh my. That was much easier. Thanks. Here are the results.

Chuck Lucas

I use a free program specifically designed for this purpose. Just wondering if anyone else has tried it. I’ve only used it a few times, but it seemed to work, and was fairly quick.

Hien Fineout

Wow, awesome blog structure! How long have you been running a blog for? you made blogging glance easy. The overall glance of your website is magnificent, let alone the content!

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