Photoshop and Astrophotography

This post isn't an assignment, but it's related to Photoshop, so I figured I would post here, so that I can share a little bit of my passion with others.

This semester, in addition to GRC183, I'm also taking an astronomy class, both to satisfy the science requisites for my GRC degree, but also because I'm an amateur astronomer, and have a love for the field. I also do a fair bit of astrophotography (though this is a relatively new thing, and I'm still learning), and I'm learning how to use Photoshop to make my images more appealing (read: less ugly). I think that, for now, a simple before and after comparison would be a good start, then I can go into the steps taken to change the original into the final product. This is still al learning experience for me, so don't expect a lot here. :)

As you can see, the image is really washed out, and has a bit of a pink cast to it. There's also very little in the way of detail within the galaxy itself. These are the areas that I wanted to address, and this is something that I explored in Photoshop. Here's the final image:

Right away, the "washed out" look and the pinkish tint are much improved and there's a little more detail within the galaxy itself, so I'm definitely getting there, though I strongly feel that I have a long way to go with the process, though for a first attempt this isn't bad at all. Now here's what I did to accomplish this.

The first thing I did was to duplicate the image so that I had something to work with for removing the pinkish tint, and much of the "ambient" light. On this duplicate image I created a selection around the main portion of the galaxy itself with the lasso tool, feathering the outline by 250 pixels (it's a huge image, so I needed a similarly huge feather around the selection). I then used the fill tool within the selection to darken and remove much of the galaxy as possible. This is because this duplicated image will eventually become a subtracting layer mask for the original image; but there are still things to do, first.

The next step was to deselect the marquee and apply a Gaussian Blur to the entire image, with a radius of 1,000 pixels (again, huge image, so huge aperture here), thus turning the entire duplicated image into a soft, amorphous gradient, of roughly the same hue as the original image's pink tint. I next added a curves adjustment layer to the duplicated image, and darkened it by 40% or so.

Ok, back to the original image. I created a new layer, selected the duplicated image and copied it, and then pasted it into the original image's new layer, setting that layer's mode to Subtract. I adjusted the opacity a little (the effect was too strong). That completed, it was time to work on the details of the image.

The next step was to make some adjustments that would improve the contrast, remove the last little bit of "washout", and bring out the colors and details. I initially tried adding a brightness/contrast adjustment layer, but wasn't satisfied with the results, so instead, I added a Levels adjustment layer, and tweaked the dark point (the left triangle, below the histogram) to line up with the spot where the "curve" of the histogram started to rise from it's minimum value. This served to deepen the dark areas of the image and to remove the last of the washed out appearance throughout the image. But the image was now rather washed out in terms of saturation, so I added a vibrancy adjustment layer, and boosted that and saturation just enough to bring out some color without making it look like a cartoon.

Once satisfied with that, I turned to the last aspect of the image that I wanted to improve: the details within the galaxy itself.For this, I used a Curves adjustment layer, raising the light curve a little at the point in the histogram where the value was peaked, and dropping the top of the line by a small fraction to keep the center of the galaxy from being overly bright. This part has proven difficult, and I don't think that I've reached the image's full potential yet, but I have yet to find the best combination of settings and adjustments that will serve me. I'll keep working on it, though, on future images. For now, this is pretty decent, so I'll leave it where it is.

I hope that this blog has helped a little with understanding at least one way of processing astronomy photographs. I didn't go into the process of "stacking" the dozens of images that this final one came from, as that's not really relevant to this blog, but at some point in the future I may start up an astrophotography blog to talk about that aspect of my life and interests. If you enjoyed this post, found it helpful, or have questions or concerns about it, please feel free to comment, below. Till next time, have fun!