Explore Landscapes #8

The workflow that I follow when shooting a star trail image can be broken down into three main steps:

1. Planning and pre-visualization

2. Shooting the timelapse images

3. Post-processing to create the final image

In this post, I go through the last step and cover my workflow for post-processing star trail images.

Post-Processing Star Trails

NOTE: The screen shots and videos in this post show Adobe Lightroom Classic v12.1, StarStaX v0.82 and I’m working on an iMac running Ventura 13.1.

Review your timelapse sequence of images one-by-one in Lightroom to see whether any of them should be removed from the stack that is to be blended. Did you shoot any test shots with different exposure settings before starting the timelapse sequence that you don’t want to include, or are there frames with stray light from passing vehicles?

At this point, I suggest you don’t delete any frames, as sometimes they may be helpful to add to the stack once you’ve seen the first version of the blended image. For example, sometimes, the light from a passing vehicle may help to illuminate your foreground (in this case), or you may have added some low-level lighting that can add foreground interest.

All of the images that you choose to blend into the initial star trail blended image should be taken with the same exposure value (aperture, shutter speed, and ISO) so that you don’t see fluctuations in the brightness of the night sky as you go through them.

Now, this next step is optional, but if you’re like me and enjoy nice clean star trails, you’ll want to remove any aircraft light trails and/or satellites or shooting stars.

Video 1 shows the process I use to remove aircraft light trails and/or other distractions in the sky. This is a little tedious, as it requires you to potentially edit each image in Lightroom, but I believe that the results are worth it.

Open the star trail images in Library and select Grid View [G]. Select the first image in the sequence and open Develop [D]. Zoom into 100% and drag the screen to find the light trail(s) [Cmd = (Mac) / Ctrl = (Win)].

Select the Healing tool [Q], and tap on the eraser symbol which is the Content-Aware Remove tool. Adjust the size of the brush using the square bracket keys [ and ] to increase/decrease the size of the brush. Change the size of the brush to the minimum size required to cover the aircraft light trail.

Move the brush over the start of the light trail and click, then shift-click at the opposite end of the trail, to connect the circle spots with a straight brush stroke. Repeat for any other light trails that you can see at the current zoom level. Click on Close (bottom right of the Healing tool bar) to confirm the Heal.

Click on Fit in the menu bar above the Navigator (top left of Develop panel) to zoom out to see the full image. If you’ve removed all the light trails then click on the next image thumbnail in the filmstrip at the bottom of the screen.

Repeat this process for each frame of the star trail sequence to remove all the light trails.

Video 2 shows how to export your RAW star trail images as TIFF files.

I use StarStaX to blend my star trail images together. It’s an excellent piece of free software from Markus Enzweiler, and is available for both Mac and Windows.

StarStaX cannot process RAW files so you have to convert them to high resolution TIFF files before you blend them together.

Open the star trail images in Library and select Grid View [G], click on the first star trail image and then Select All images [Cmd A (Mac / Ctrl A (Win)].

Export Images [Cmd Shift E (Mac) / Ctrl Shift E (Win), select (or create) an export preset for a full-size TIFF, with no compression, ProPhotoRGB, and 16 bits bit depth, and click Export.

Lightroom will then create a TIFF file for each of your RAW star trail images.

Video 3 shows how to blend the individual star trail images together to create the star trail timelapse as one single image.

Open a Finder (Mac) / File Explorer (Win) window next to the StarStaX window so can see both of them on your screen at the same time. Click on the first exported TIFF file and then Select All images [Cmd A (Mac / Ctrl A (Win)].

Drag and drop the TIFF files into StarStaX - then release the mouse to load the TIFF files.

The default blending mode is Lighten - and that’s the setting I use for almost all star trail blends. If you want to check that Lighten has been set as the blending mode, or you’d like to experiment with the other blending modes, then click on Blending in the RH Preferences panel and in the dropdown select your preferred blending mode.

Click on Start Processing (4th icon from the left, top LH corner of screen) and StarStaX starts blending the images and your star trail begins to appear.

When the blending has finished click on OK and then click on Save As (3rd icon from the left, top LH corner of screen) and select the folder to save to - making sure that you change the filename type to tif to create a TIFF file.

NOTE: I import all of my TIFF files (both the initial TIFF versions of the RAW image files plus the final blended TIFF file) into Lightroom. This gives me the option to rework the image in StarStaX at a later date if I want to without having to recreate the TIFF files from scratch.

Video 4 shows how to edit the blended star trail TIFF image to remove any hot pixels and/or other distracting elements.

Open the StarStaX blended TIFF file and go to Develop [D]. Zoom into 100% [Space] and drag the screen to find any hot pixels (bright white individual pixels that may be present in the dark areas of your image).

Select the Healing tool [Q], and tap on the eraser symbol which is the Content-Aware Remove tool. Adjust the size of the brush using the square bracket keys [ and ] to increase/decrease the size of the brush. Change the size of the brush to the minimum size required to cover the hot pixel.

Cover each hot pixel in turn with the brush and click to remove. Repeat for any other hot pixels that you can see at the current zoom level. Click on Close (bottom right of the Healing tool bar) to confirm the Heal.

Drag the zoom window around the image to look for any more hot pixels and repeat the steps above. Click on Fit in the menu bar above the Navigator (top left of Develop panel) to zoom out to see the full image.

And there you have it - a completed blended star trail image.

If you have any questions on my workflow or any other topic I've mentioned, please leave a comment below, and I'll get back to you.

Until next time, explore, experience, and enjoy our wildlands responsibly. Think before you geotag. Adopt the 7 Principles of Leave No Trace and practice Responsible Nature Photography.

Bye for now,
Jon