Editing Astrophotography in Photoshop

How to Edit Astrophotography in Photoshop

Astrophotography is a unique type of photography that describes taking photos of the night sky, including photos of planets, the sun, the moon, galaxies, nebulae, the milky way, and starscapes.

While some astrophotography involves advanced telescopes and cameras, you can also take great photos of the night sky using only your camera, camera lens, and tripod.  What equipment you use just depends on your budget and what exactly you want to achieve.

There are several stages of astrophotography including:

• Planning the image
• Setting up equipment
• Capturing photos
• And post-processing

In this tutorial, I will show you how edit your Astrophotography images in Photoshop to really make them POP like my before and after galaxy photo below! 

Let's get started.....

1. Stack Your Images

Keep in mind, that the "before" photo shown above is NOT my straight out of camera photo.  Astrophotography involves taking several long exposure photographs and then stacking those photos to reduce noise and enhance detail.  Personally, I use Astro Pixel Processor to stack my photos.  Another good program is Deep Sky Stacker - its simple and FREE, but is currently only supported on Windows.

2. Levels Adjustment

Once you are satisfied with your "stacked image", bring it into Photoshop and make sure to duplicate your background in case you need to return back to it and start over.

You will want to start off your Photoshop editing by adjusting levels.  Specifically, I recommend bringing in the black point to where the data starts, and you will want to bring your midpoint in to brighten the galaxy.

3. Curves Adjustment

Once you are satisfied with your levels, lets make some Curves adjustments.  Curves are often used in editing astrophotos to stretch the data.  In this case, I am going to use an S curve to enhance contrast.

To do this, grab the selector icon in the bottom left of the curves tab and sample two parts of the image: the galaxy, and the background.  Drag the galaxy upward and the background downward.  This will create a nice S shape in the curve.

4. Star Minimization

Next, I want to do some star minimization.  What?!  Why would I do want to minimize stars in a space picture?

Stars are very bright and they can often be so densely clustered that they interfere with the details of the galaxy or nebula that you want to highlight in your photo.

In order to minimize the stars, you will need to create a star mask by selecting ONLY the stars in your image.  To do this, first go to the "dust and scratches" tab and move the slider until you have blurred all the stars out.  Next, change your image blending mode to subtract.  This will create a photo of only the stars in your image without affecting the galaxy OR background.

Now that you have your star mask you are going to want to make a selection of the stars and then minimize them. To do that, go into the color range tab.  Select highlight and use the sliders until you have most of the stars selected. 

This typically does a great job of selecting the stars, but you also may have to expand and/or feather your selection to select them without having rigid edges.

Now that you have your selection of stars, go to the minimize tab and use the slider there until you are satisfied with your star size.  Be careful and deliberate with minimization becaue if you use too much, it will leave artifacts on your image.

5. Color Adjustment

Color enhancement plays a big role in editing astrophotography images.  Even though the color difference may be subtle, it will make your image much more interesting and eye-catching.

There are many ways to edit color in Photoshop but I typically use the Vibrance tab.  You will want to increase the vibrance and saturation in your image to a point where it’s NOTICABLE but still looks REALISTIC.  If you go overboard with your color adjustments (which is easy to do), your photo will look severely overprocessed.  As I mentioned before, just keep it simple and realistic for best results.

6. Noise Reduction

The final step in my processing is noise reduction.  It is VERY COMMON for astro-photos to have a lot of noise, even after stacking.  The long exposures and high ISO settings used in astrophotography cause the temperature of the camera sensor to heat up quickly and result in noise.

To reduce noise, go into Adobe Camera Raw and select the details tab.  Under details, you will find noise reduction.  You won’t need to apply much of this effect because it is strong and can destroy the fine details of your picture.  After reducing noise, if I notice that I lost some details too, I will usually sharpen my image using sharpen slider (which is also found under the details tab).

Your image should now be complete and looking beautiful yet still natural!

Conclusion

Post processing in Photoshop is my FAVORITE step of Astrophotography.  Its where I finally get to see the beauty of my photo unveiled.

Remember that it's VERY EASY TO OVER-PROCESS ASTRO-PHOTOS.  I can’t stress this enough!  Stars, planets, galaxies, etc are real and should only be enhanced, not manipulated.