For the post-production of images of the Milky Way I use various methods. This tutorial can be applied to edit a 32-bit image or a Raw file directly in Adobe Photoshop CC with the help of our plug-in “Astro Panel 3.0″ can you shop here.
For 32-bit images, those generated directly in the source folder by the “Deep Sky Stacker” software, I prefer to use this file without modifications and manage it in Photoshop. For RAW files the situation is different because it is managed directly by Adobe Camera Raw and opened in Adobe Photoshop CC. The tutorial is identical and differs only in the use of the 32-bit command. For RAW files it should not be used because they are already in 16-bit. Open the file “Autosave.tif” generated by Deep Sky Stacker to manage it in Photoshop. The first thing to do is transform the image from 32 bits to 16 bits by clicking on the command “32 – Convert from 32 to 16 bit image (DSS)”.
The next step is to reset the colors and decrease the green cast in the image. The commands to use are RC – Reset colors Astrophotography and RG – Remove Green color.
Clicking on the command RG – Remove Green color, the background is duplicated and we can adjust the opacity to achieve the desired result and after arranging the tones and adjusting the green cast, we merge levels. Let’s analyze our image by looking at the histogram at the top right. This analysis is necessary to switch to the other group of commands and understand which function to use. We will use “Streching Image”, which brings out the hidden signal present in the Milky Way and to give more contrast to the image. Click on the “SD” button which is used for underexposed images (as in this case). Use the “SB” button only if your image is overexposed. You notice this because the histogram is more skewed to the right, as opposed to what we have in the current histogram.
If the result does not satisfy us, we can always use the curves to darken the image. We proceed as illustrated in the image and with the hand we darken the image.
Click on Merge Levels and continue. The next step is the reduction of chromatic noise and digital noise present in the image. To do this, we can use the group of dedicated “Image Correction” functions and click on the “NS – Noise Reduction Soft” noise reduction function to give a soft effect. We adjust the opacity of the duplicated layer to preserve details.
As you can see, we have adjusted the color noise and digital noise in one single click. If the result is satisfying, click on Merge levels. Otherwise, if it is not enough we have another “NH” command that applies noise reduction more aggressively. We have other tools at our disposal, but for now we will not use them.
You have noticed that I have missed two groups of functions: “False Flat” and “Star Tools“. These functions are not recommended for the Milky Way, but are indispensable for the post production of deep sky images. The next step will allow us to extract even more signal from the Milky Way and increase the contrast of the galactic clouds and of the overall image. We are talking about the “Enhance” commands. We execute the command “EL – Enhance Luminosity” and immediately after “EN – Enhance Nebulosity“. The first “EL” command aggressively performs its work, while the second needs to be pressed 2-3 times to see its effect.
The advice I give you is to work step by step to achieve a satisfactory result without producing artifacts and destroying the detail of the image. Speaking of detail, let’s move on to the next level: “Sharpness“. This allows us to extract the detail in two ways, fine and general. In our case we will use the command “PB – Precision Boost” to highlight the milky way filaments with a brush and then a touch of “HP – High Pass Filter” to contrast the general detail of the image.
At this point, we can start working on color with the help of the “Color Balance” and “Tools” commands. The command “SCO – Selective Color Milky Way” helps us to adjust the colors of the Milky Way. If the result is not satisfactory, or the colors are off, on the right we have the “Color Boost” group that livens up the colors in Color Lab. In our case I used the “LL – Color Boost Low” function because the colors were not very saturated, as you can see in the image below.
For the “Tools” section, that includes color and luminosity masks, I invite you to follow the video tutorials online, as it is very complicated to describe their use here. In this case, however, we do not need the masks and we make the final touches to the image using the “Fine Tuning” group of functions.
Analyzing the image, I proceed to click on the “CI – Contrast Image” and “OR – Orton Effect” commands to make the latest changes. Adjust the opacity of the effects to chieve your result.
As you have noticed, we have obtained a satisfactory result, without creating artifacts, maintaining remarkable details and correct colors, in just a few minutes and with the right controls.
On the following page you can view the before and after of the image just processed.
Thanks for reading.