Embedded Files
Halpha Layer Group
Halpha Layer Group
Next, we'll add Halpha data to bring out the nebulae in M51. We'll show them as pink regions.
The bottom layer (Ha.tif) is the Halpha master.. Above it is RGB_R.tif, the extracted red channel. RGB_R.tif is subtracted from Ha.tif so that only the true Halpha signal remains. Levels adjustment layers above each let us fine-tune the contributions of each. A Hue/Saturation layer rests on top to add color.
The entire layer group is put into "screen" blending mode, meaning it will only be visible when its content is lighter than what's below it.
Finally, a mask on the entire layer group limits it's effects to the body of the galaxy.
Ha.tif: the Halpha master.
RGB_R.tif: the extracted red channel.
The result when red is subtracted (using "subtract" blending mode) from the Ha.
The Halpha layer after subtraction and colorization.
Hue/Saturation 3: click on "colorize" to add color to a mono layer. I've adjusted the Hue slider to create a pink color that blends well with the original RGB data.
This mask, when applied to the entire layer group, only allows the Halpha data to come through in the galaxy core.
The group, once the mask s applied.
Our image without adding Ha.
After adding Ha to bring out the nebulae.
Global Adjustments
Global Adjustments
These adjustment layers will affect the entire image. We'll increase contrast and saturation, tweak the color balance, add some pop, and brighten any black pixels. That will smooth the background and hide some noise.
Notice that some adjustments are targeted to specific areas using masks.
Levels 6 slightly darkens the blacks.
Some areas of the galaxy are masked out and won't be darkened as much.
Curves 1 add some contrast to the galaxy.
Its layer mask limits the effect to specific parts of the galaxy.
Hue/Sa...tion 5 with adjustments to overall saturation and targeted adjustments to yellows, cyans, and blues.
After hue/saturation adjusments.
Color Balance 1 helps tweak the blue color of the spiral arms.
After color balance with the adjusments limited to the galaxy by a mask.
Two color dodge layers add some pop to the image. First, create a solid fill layer with a dark color, in this case 15-15-15 (almost black).
Then set the layer to "color dodge" blending mode. This image benefited from 2 applications of this technique.
We don't want any pixels to be completely black. We can fix any black pixels by creating a solid fill layer with a dark, but not black, color. Here the color has RGB values of 19-19-19.
Finally, we'll set this layer to "lighten" blending mode and name it Color lighten. Now, any pixels darker than 19-19-19 will be raised to that tone.
Before global adjustments are applied.
After global adjustments.
Adding Stars
Adding Stars
There aren't many stars to worry about, and they're sitting on top of everything else in their own layer group, which is in "screen" blending mode. We will make a couple tweaks to tighten them up and bring out their color.
First, we'll convert the STARS layer to a smart object, allowing us to tweak any filters we apply later on. In this case, we'll use the Camera Raw filter to apply a bit of sharpening to the star edges.
A look at the stars at a zoom level of 270%.
Stars after sharpening.
The sharpening settings. I want to apply sharpening without creating super-crisp edges.
A slight adjustment to the midtones slider reduces a bit of fuzziness at the edges of the stars.
Star colors lose some color depth in screen blending mode, so we'll compensate by applying a bit of saturation. Here is the overall saturation adjustment.
The same adjustment layer, but with a slight reduction to red saturation, reducing the dark red fringes around some stars.
We'll also enhance the yellow tones.
Final Result
Final Result
Here we can see the transformation from 1 individual subframe of 30 seconds to a final image that includes over 18 hours of combined data, shot using two different cameras over two years.
Several hundred individual subframes went into this project.
I hope to capture more data in the future, which should allow me to bring out even more of the faint tails surrounding these two colliding galaxies.
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