Image Processing for Nebula Object

There are so many ways to make astro images from Raw File .

Here is one way using RawDigger + Photoshop.

I used RawDigger to extract the original color data before [Bayer Image processing] by Canon.

For Tiff file export, it’s need to choose Research Edition.

Open  CR2 File in RawDigger program.

File > Export Tiff

Please check  [Export Options] and set as below screen shot sample.

Bayer processing option [half size] is important to get real color data that camera caught. I think in the work for indistinct nebular object, valid color data is more precious than image resolution.

Save the file as a new named file. Then you can get 3000×2000 image.

Repeat [open > Export] to all CR2 file.

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These files are nearly black images, but  don’t worry. It’s caused by 16bit unprocessed color palette per each channel.

If we stack these files in Photoshop, we can make so valid color image.

Load one Dark frame shot file.

 

Export Dark frame Tiff file as above light shots.

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Start PhotoShop program

Open Dark Frame Tiff image.

Save Dark image to Clipboard: = Ctrl + A (select all) , Ctrl + C ( Copy)

Open first Light Image Tiff File.

Paste Dark image to first Light image: Ctrl + V ( Paste)

You can see  [Layer 1] above [Background] layer

Change Layer option of [Layer1] : Normal to Difference

Flatten the layers : (=Dark frame applied to light image.)

Save first light image applied dark frame subtraction with a new name.

Close first light image Tiff file.

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Open second light image Tiff file.

Paste Dark image to Second Light image: Ctrl + V ( Paste)

Change Layer option of [Layer1] : Normal to Difference

Flatten the layers : (=Dark frame applied to light image.)

Save Second light image applied dark frame subtraction with a new name.

Close Second light image Tiff file.

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Repeat to Last light imge Tiff file. : Dark Frame subtraction finished.

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Make a New 16bit photoshop file [Untitled-1] that 110%~120% size of Tiff light image.

Open Dark Frame applied [first light Image].

Select all image of Dark Frame applied [first light Image] : Ctrl + A (select all) , Ctrl + C ( Copy)

Paste Clip board image to[Untitled-1] psd File. : Ctrl + V ( Paste)

 

Close [First light image] and Do not close [Untitled-1] psd File.

Open Dark Frame applied [Second light Image].

Select all image of Dark Frame applied [Second light Image] : Ctrl + A (select all) , Ctrl + C ( Copy)

Paste Clip board image to[Untitled-1] psd File. : Ctrl + V ( Paste)

Change [Layer2] options : Normal to Difference

Move [Layer2] carefully to be completely overlapped over [Layer1]. : You can see all black image without any blight points.

Change [Layer2] options : Difference to Linear Dodge (Add) : This is Image stacking mode

Change [Layer Visibility] of [Layer2] to [Off]

Close [Second light Image] Tiff file  and Do not close [Untitled-1] psd File.

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Open Dark Frame applied [Third light Image].

Select all image of Dark Frame applied [Third light Image] : Ctrl + A (select all) , Ctrl + C ( Copy)

Paste Clip board image to[Untitled-1] psd File. : Ctrl + V ( Paste)

Change [Layer3] options : Normal to Difference

Move [Layer3] carefully to be completely overlapped over [Layer1]. : In case of good alignment of images, you can see nearly black image without any blight points.

Change [Layer3] options : Difference to Linear Dodge (Add) : This is Image stacking mode

Change [Layer Visibility] of [Layer3] to [Off]

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Repeat to Last light imge Tiff file. : Image stacking finished.

Change [Layer Visibility] of all layers to [On]

Save file with the name [light_stacked_all.psd]

Menu>Layer> Merge Visible

You may meet an image that color balance was broken. But don’t worry.

Menu>Image> Levels

Change [Levels] options as below.

Target Colors & Clipping > shadow  Clip and Highlight Clip values will be your choice in the range 0.1~9.9

Menu> Filter> Blur > Gaussian Blur

Adjust pixel Radius of Gaussian Blur. This will make smooth gradation in the star and reduce background noise ,I recommend 0.3~1.5pixels range.

Please do your work, if you want to. Brightness/ Contrast, Levels, Curves..

 

Image Processing is finished.