Introduction
In this short tutorial I will try to explain how to create a star trail in Photoshop.
We will use an automatic procedure that will convert our night shots (sometimes a big number!!!!) in a single composite image.
The Most Common Method
The most common method to create a star trail is to download some freeware software like startrail or starstax.
These tools offer different effects but none of them allows us to use the potentialities of Adobe Camera Raw or Photoshop. The first one do not use 16 bit files, the second do not permit to use raw files (at least until the moment when I am writing this article). In any case, here are the links to the softwares:
Startrail: http://www.startrails.de/html/software.html
Starstax: http://www.markus-enzweiler.de/software/software.html
The First Step in Adobe Camera Raw (ACR)
If you like to retain the full control on your files and want to spend the right time to obtain the best results from your night photographic session, here is for you the long way.... I assume that yours are raw files that need to be processed in ACR.
First thing to do is to set the default parameters for the raw processing in ACR. This parameters will be applied to all single raw file in order to have images that are coherent each other’s in terms of white balance, shadows and highlight handling, noise reduction and so on. (fig.1).
Star Trail in PS - ACR fig.1 - Star Trail in PS - ACR fig.1
Fig.1
To save the settings let’s open the menu clicking on the small black arrow (top right upon the white balance slider). Then save settings with the name that you like e.g: star trail (fig.2)
Star Trail in PS - Save Settings fig2 - Star Trail in PS - saving settings fig.2
Fig.2
I really recommend not to correct for your lens profile except for chromatic aberration otherwise you will face unwanted artifacts. From now on, any raw image will be opened with our default parameters.
Once saved the settings we need to say to ACR that these are default settings. In the same menu just select Save New Camera Raw Default (fig.3).
Star Trail in PS - Save Default Settings fig3 - Star Trail in PS - saving default settings fig.3
Fig.3
The first step in Photoshop
At this point we need to create an action in Photoshop that emulate the workflow for the star trail creation. Here is the procedure:
1. keep your raw files in a single folder;
2. open the first raw file and enter Photoshop from ACR;
3. convert it in a RGB color space by Edit > convert to Profile choosing whatever RGB color space you like (e.g: Adobe RGB);
4. Open the second file of the star trail (same procedure of point2);
5. Open the menu actions from Window> Actions;
6. Then create an action cliccking on the small icon of fig.4 (bottom right);
7. Give a name to your action;
8. Then click record to record the following steps (fig4).
Star Trail in PS - Create the action fig.4 - Star Trail in PS - Create the action fig.3
Fig.4
1. On the second file select all;
2. Copy and paste on the first image;
3. If the source and destination clor space are not the same PS could ask you what to do. Answer covert and check the little box do not ask again;
4. The first image now has two layers the background and the layer 1;
5. On layer1 select the blending method lighten; a small trail have been created!!!!
6. Merge down the levels;
7. Select all;
8. Copy and paste on the second file;
9. Merge down the level on the second file;
10. Stop the recording (first button down on the action menu).
Now Photoshop needs to:
• Open one by one your raw files;
• Apply the default ACR settings without opening ACR;
• Apply the recorded action to create step by step the star trail;
• Save every single file once it has created the star trail.
The star trail will be created on the first file, copied on the second and saved. The first file remains open to receive another little piece of star trail….and again….
Photoshop and the image processor
1. Let’s close all the opened files in PS;
2. Open the first file of the star trail (very important step);
3. Open the image processor File > Scripts > Image Processor (fig.5);
Star Trail in PS - Image Processor fig.5 - Star Trail in PS - Image Processor fig.5
Fig.5
Now we are inside the image processor module
1. On section1 select the folder containing the source file (your raw files);
2. On section one remove the check on “open image first to apply settings”. The ACR module will not be opened but your default ACR settings will be applied;
3. On section 2 select the destination folder;
4. On section 3 select the way you want that PS saves your files;
5. On section 4 select the action the creates the star trail;
6. You can decide to apply your copyright;
7. Select the little box to apply ICC Profile fig.6.
The most important options are the one inside the blue circles.
Star Trail in PS - Image Processor details fig.6 - Star Trail in PS - Image Processor details fig.6
Fig.6
The final result
At the end of the process, you will get lots of file each containing a star trail. Every star trail is a little bit longer then the previous one.
The first one is just a star field, the last one is your final star trail. These files can be used to create a time lapse with the trail like this one:
http://www.dariogiannobile.com/time-lapse/h1836f249#h1009b9ce
or this:
http://www.dariogiannobile.com/time-lapse/h1836f249#h1836f249
If in the Image Processor module you do not select the action you will simply convert your raw files in JPG or TIFF or PSD without opening every single shot in ACR. These files can be used to create the most common time lapse like this one:
http://www.dariogiannobile.com/time-lapse/h1836f249#h13efbae8
You can even decide to create your star trail action with inside some regulations and filters such as curves, saturation, unsharpening and so on.
Conclusions
Even if the procedure could appear a little bit complicated, once you go through it for the first time it will be very simple indeed. It is required a little effort to create the action but then i twill be available for all your next stra trail and you do not need to do ita gain everytime.
On the other hand you will get the full control of your file using all the power of ACR and PS as for image below (fig.7) and your workflow will remain inside PS without changing software.
Star Trail in Photoshop - the missing observer fig7 - Once the courtyard of our farmhouses were places where people met and talked about the strenuous day of work in the fields. May be they stayed sit looking at the clear and dark sky. nowadays these places are abandoned and no one is looking at the sky any more. That's the reason why the chair is empty and the mirror reflects the sky the the missing observer would have looked at.
Fig.7
http://www.dariogiannobile.com/sky/startrail/h2e3b828b#h2e3b828b
Do not forget that even the best shot you can do will not compete with the nature show itself!!
If you think that this Tutorial could be useful to other astronomy and astrophotography amateurs, please feel free to share it!!
"...It often seems to me that the night is much more alive and richly coloured than the day..."
Ciao
Dario
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