"For He hath looked down from the height of His sanctuary; from heaven did the Lord behold the earth;"

Psalm 102:19 KJV

In this continuation from my previous article, Letting The Light In: Going Deep - Part 1, I wanted to share more of my journey with Deep-sky Photography and the parallels I have found with The Word of God and how it has really brought a humble appreciation and awe of The Lord's Glory all around us and particularly in the experience of photographing the night sky.

Having touched on the different components of how to set-up a shoot of deep sky objects, and the workflow I have personally found of benefit to me, I wanted to spend the next few remaining sections on the process of "photo stacking" the images to bring out light and detail that simply cannot be obtained from one shot.

So a quick recap: I have finished taking my sequence of images of light frames, dark frames, bias/offset frames and flat frames - and must now upload them to my computer and process the images. To do so, there are as mentioned special programs/apps like Siril or DeepSkyStacker that can be used to do this. I will be using the program Siril, and with that taking all those recorded images and cramming them into one usable, editable image for my final shot.

As the stacking process can get varied and technical, I will defer a tutorial on the specifics of Siril to the many how-to videos online, but here are the basics:

The sequence of frames are in their own home directory, and in that directory is a specific order of folders, named in plural: biases, darks, flats, lights - they must be in this exact order top to bottom for the process to work correctly.

Then a click on the home button in the upper left corner of the screen to establish or change our home folder so that we are drawing from the directory we have our various folders in. (You'll see it listed at the top of the screen as well)

Then we click the "Scripts" pull-down button (to the right of the home button) to run an automatic script program called OSC_Preprocessing. (this can also be done manually for more fine tuning but definitely watch a video for that) Doing this, you will now see a rundown of text as all those images that night are thrown in there and compiled to produce the very image we will be using for the final edit. This may take a few minutes depending on your computer set-up.

Once it finishes, we are left with a TIF file with the name "result" that we will then use in a process called "stretching." For this we click the "open" button in the far upper left corner and click ok. From there, click on the "linear" pull-down button at the bottom of the screen and select the "AutoStretch" option. Then right-click on the image and select "Crop" to reframe your image. Examples of before and after crop below.

Then we go to "Image Processing" at top left, pull down to Background Extraction, and click "Generate." if any of the little boxes show on the object, remove them, and click the "Compute Background" button then click "Apply."

Then we adjust the color, click "Image Processing," "Color Calibration," "Photometric Color Calibration." Then you search for the object at the top under "Image Parameters" and click on the selection, then "Get Metadata from Image." Then finally, click "Ok."

Now we go back to the "AutoStretch" button at the bottom and click back to "Linear."

At the top of the screen, click the "Image Processing" pull-down and go to "Histogram Transformation." In that box you'll see a button under the histogram at the right that looks like a gear with a wavy line through it. Click that for the "AutoStretch" Algorithm and click "Apply."

Now repeat by going to "Image Processing" pull-down again and go to "Histogram Transformation." Now you can fine-tune the image by moving the lever directly under the Histogram. Then click "Apply."

Finally, go to "Image Processing" like before but this time select "Color Saturation." Adjust levers to your preference, and click "Apply."

Now I can edit this further in Adobe Photoshop, and all this work comes to my final image below.

What a rewarding experience this was! All those hours and effort and patience, and yet all I remember looking back is the quiet solitude of being with my Lord Jesus looking at His Glorious Creation in the heavens during that night. Words cannot describe... The thing about the Photo Stacking process, and hence the very title of this series, "Letting the Light In: Going Deep," is that there is such a parallel to Deep Sky Photography and reading the Word of God; His Holy Bible, for me...

No matter how many times I may read a particular chapter or a particular verse, each time it's like something new is brought forward. Read by read, stack by stack, brighter and brighter, bringing out further and further detail. Something I didn't see or realize before. It can be a lesson I didn't catch prior to that. A reminder of God's Instruction I didn't grasp the last time. An encouragement from the Lord I needed right then and that could not apply the same way at another time. Absolutely Incredible The Lord God Is... 

Thinking back to what I mentioned earlier in the previous article, this is an experience that again reminds me of how GREAT God Is. How Great His Power. How Great His Majesty. How Great His Love. And how very very small, I really am...

Until next time...