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2017 07 07 - Just One Click – Botallack Star Trails pt2

Welcome to part two of the first article in my “Just One Click” series, where I delve into the making and taking of some of my photographs. In part one I discussed location selection, equipment, and camera set up, as well as taking you through the shooting process needed to get a set of photographs to process into your finished image.

It is in this part where your image is truly brought to life. The individual photos will be layered, the pin point so the stars will become trails, and you will give the foreground the light that it deserves.

This stage will take several hours, requiring some heavy processing from your computer. Because you will be working with whole sets of photos in one go, your computer will need at least 8gb of RAM as well as plenty of disk space. The files generated by this process can be several gigabytes, so make sure you have the space before you start!

Following this workflow will yield great results, however there are other methods and other software that will automatically stitch these shots. I tend to avoid these as I prefer the control that Adobe Photoshop gives me, and the extra effort gives better results, making it easier to remove imperfections caused by stray light.


I use the following software combination to get the best results. There are plenty of other methods for doing this, however I am very pleased with the results that I get.

*Adobe Bridge – file management

*Adobe Camera Raw – initial corrections

*Adobe Photoshop – layering and final adjustments

*Nik Tools (now free!)

The Adobe products are available as part of the photography Adobe Creative Cloud subscription found around £7 per month, exceptional value for money!

The Workflow

Your workflow will follow these steps

*Copying images to a folder on PC

*Initial processing of the images in batches using Adobe Camera Raw

*Layering in Adobe Photoshop

*Removal of unwanted elements

*Stitching the foreground

*Final processing

This isn’t a complex workflow at all, and the layering is really simple.

Copying the files

Copy the files to a folder in your usual photo directory. Depending on how many shots you took and how epic your computer is, you will probably want to process the shots in batches, however, the initial stage of processing the RAW files should be done as a single group so that the exposures and contrast adjustments are matched. So, initially, place the RAW files into two folders. Those that you took for the foreground, and those that you took for the stars.

Processing the Stars

Open Adobe Bridge and go to the folder in which you saved the star RAW files. Select all of the files and open them in Adobe Camera Raw (ACR). When ACR loads, all of the star shots will be present as a list down the side. At this point, select all of the individual photos so that you are adjusting them all. I tend to make very subtle adjustments at this stage with a mind to bringing out the stars and reducing noise in the image. Do not hit the “Auto” button at this stage as you will get some nasty results

We are editing these photos for the star trails portion of the image. Remember that we are going to be layering in the foreground from your foreground specific shots, so don’t worry about what your adjustments are doing to that area of the image.

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This image shows all of the images selected in Adobe Camera Raw

For this photograph I added a simple curves adjustment. With all of the photographs in the series selected, I then clicked to the curves tab and added two points to the line, and dragged them to increase the contrast in the shot. Everything else remains as shot in camera. I didn’t feel the need on this shot to do any noise reduction.

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A simple subtle curves adjustment in Adobe Camera Raw

Now that you have made the contrast and noise corrections, close Adobe Camera Raw. The adjustments will be saved automatically in an “.xmp” file so that when we open the images in Photoshop we are ready to go.

Depending on how good your computer is, you can no opt to process all of the files in one go, or in batches. My PC is a fairly modern Intel i7 with 32gb of RAM and solid state disks, and it struggles to open the 200+ 86mb RAW files that my camera produces. It does it, but it makes the computer sweat! You will need to decide whether your computer can cope with this! I will assume that you are opting to process the files in batches as that is the slightly more complex work flow, so best that I describe it.

Go to the folder on your computer, and create a set of folders for each batch of files. “Batch1”, “Batch2”, “Batch3” etc. Move the RAW files and their xmp files (these were created when using ACR above) into the folders in whatever batch size you decided. E.g. Move 20 files into the first folder, then next 20 into the second folder, and so on. When you have done that, you are ready to go on to the Photoshop stage. This stage is exactly the same whether you are processing all of the images in one go or in batches.

Layering in Photoshop

Go back into Adobe Bridge, and move into the “Batch1” folder. Select all of the files, and then go to Tools–>Photoshop–>Load Into Photoshop Layers

This will now load Photoshop and begin loading all of the files into the new file sequentially, adding each photograph into its own layer.

When this is done (it can take some time), select all of the layers by clicking the top layer, holding down shift, and then clicking the bottom layer. Now change the layer blending mode from “Normal” to “Lighten”. The blending mode changes how Photoshop views the image. In Normal mode, only top layer is visible. When you change to Lighten Photoshop combines all of the light points of the image, allowing the stars, which are light, to shine through each layer. You should instantly see the star trail starting to form.

You may also see some unwanted elements in the image, straight lines of light, or car headlights lighting up the image where you don’t want it. It is best to edit these out now, rather than trying to fix them in the final image. The editing is very easy, but a little repetitive.

Removal of unwanted objects

You probably noticed while you were taking the photographs that the nights sky is not a still and quite place, rather it is filled with objects zipping about. You will have planes and satellites flying across the sky, maybe the International Space Station. If you are on the coast there will be boats lighting the horizon. A car may have driven by, lighting up your foreground, or even catching the front of the camera in its headlights. All of these will need to be removed otherwise they will be visible in your final image. See the image below for an example of what to look for.

Unwanted objects in the star stack, caused by boats and satellites.

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The passage of the satellites/planes will likely have been captured by several of your photos as they cross the sky. The best way to fix this is in each individual photo.

*Select all of the layers in your file

*Change the blending mode back to “Normal”.

*Now, working from the top down switch off the layers until you find the one with the offending light.

*Add a layer mask to the layer.

*Select the layer mask

*Select a brush tool, and set the size so that it just covers the light you want to remove.

*Set the brush colour to be black, and the opacity to be 100.

*With the mask selected, paint over the light with the black brush. You should see it disappear. This is because the area that is black in the layer mask is now transparent, and you are seeing the “clean” layer below.

*Switch off this layer and move onto the next, repeating this process until all of the layers are free from lines of light that you want removing.

*Now select all of the layers again and set the blending mode back to “Lighten”. All of the lines of light should have disappeared, leaving you with nice star trails.

*Save this file into your “Batch1” folder as a .psd file.

Star Stacking

We will now flatten this into a single layer, so that we can merge it with the other batched images later. Select Image–> Duplicate Image from the Photoshop menus. This will open this as a separate file. Now, right click on the layers area and select “Flatten Image”. All of the layers will go, being replaced by a single layer, showing the star trails that you have been working with. Save this as a psd file into a new folder called “Flat Stars”, calling it something like “Batch1_flat.psd”.

Flatten Batch 1

Repeat this process for each of the batches that you have been working with. By the end of it you should have a clean psd file in each batch folder, and a set of psd files in the “Flat Stars” folder, one for each batch.

If you processed all of the files in one go, great!

You can ignore this next simple stage. Go back into Adobe Bridge, and navigate to your “Flat Stars” folder. Select all of the psd files that you see there, and click “Tools–>Photoshop–>Open in Photoshop Layers”. Now, exactly as we have done before above, select all of the layers and change the blending mode to “Lighten”. You should now see the final results of your labours, a full swirl of star light. If there are still stray lines of light in your shot, you will need to identify which batch they are coming from, and go back and fix them. When you are happy that your image is clean, you can flatten the layers, and save this into the main folder as “Stars.psd”.

Merge Batches

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The stars photos have all been blended now

Processing the Foreground

Go back into Adobe Bridge and navigate to your foreground images folder. Select the best foreground image you have got. Remember that the stars are going to be fairly dark so you are looking for a foreground shot that isn’t a million miles away in terms of exposure. You don’t want the foreground to appear unnaturally bright, but it needs to be light enough that you can see what is there.

Open the shot you selected in Adobe Camera Raw and make adjustments. You will probably want to lower the exposure a bit, to make it match the stars, and increase the contrast. It may also require some shadow adjustment. Remember, you are trying to get this to stitch into the stars at a similar exposure, so you may need to flick between ACR and Photoshop (where your star photo should still be open) to compare the two. Once you are happy, click the “Open” button in ACR. Save this file in the same location as you saved your “Stars.psd” as “Foreground.psd”. We are now going to layer this image and the stars together. There are various ways of doing this, but we will repeat what we have been doing above.

Close both of the Foreground and Stars files, saving them both if prompted.


Go back into Adobe Bridge, and find the folder that contains your “Stars.psd” and “Foreground.psd” files. Select both of these files and click follow the “Load in Photoshop Layers” procedure that we have been using up until now. Photoshop will open and you will have a file with two layers, the Stars and the Foreground. Change the layer order (drag the layer) so that your stars are the top layer, the foreground the bottom layer.

Align the images by selecting both layers, then going to “Edit–>Auto-Align Images”, and selecting “Auto”.

Add a mask to the stars layer. Leave the mask white. Now, use the “Quick Selection” tool, to select the edge of the foreground elements where they meet the stars. You will need to be quite accurate with the masking in order to make the blending neat. Once you have selected all of the foreground area, click on the layer mask, and then using a large black brush at 100% opacity, paint over the foreground. You should start to see the foreground from the foreground layer starting to show through.

When you have fully painted out the foreground area in the stars layer, we can deselect the selection. Click back on the select tool, then right click on the photo, and “deselect”. You will probably notice that the margin between the foreground and the stars layers is quite harsh. You may also want to retain elements from the stars layer in the foreground, if you feel they give the image a better look. To correct the blend line, we can set the brush to white, and the opacity to around 5%. Click on the mask, and then paint over the photo where the two layers are blending together. You will need to go over the area several times to more subtly blend them together, moving all along the blend line where the stars meet the foreground.

Blending Foreground Edit

Final adjustments

Once you are happy with the blend line, we can use the various adjustment layers in photoshop to finish the photo off. If the foreground isn’t quite matching the exposure of the stars layer, we can adjust this independently by adding adjustment layers that only affect this layer. We can do likewise with the stars.

My final step tends to be making use of the excellent Nik Collection suite of tools. This is a free plugin to photoshop that gives some amazing results. If you haven’t got it already, I recommend installing it.

For the star trails shots, I tend to follow this simple work flow with Nik tools.

*Viveza –> increase structure, and adjust the brightness and contrast if the image needs it.

*If the foreground is noisy, use the Define tool, then add a mask to this layer. Paint black over the stars area of the image, so that you see the “structured” level below.

*Now, sharpen the image.

Save! You should now have a beautiful star trails photograph to be proud of!

Finalise Edit

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