washing the dust of daily life

I thought I would take a photograph of the moon. The project has turned out to be more involved than I had expected, but that's only raised my interest. The image above is my third attempt with some sophisticated tools, but not my last.

In my camera the moon is terribly small, but for this image I used a old 1982 Tasco F-9 800 mm with a 2x eyepiece & camera attachment. I got the telescope free from a friend and only had to buy a Nikon T-mount adapter.

My digital camera set to manual exposure, I experimented until I found 1/20 sec, ISO 800 gave the best exposure; the telescope labels indicate f/15 and 2400 mm, but it is hard to say for sure. And I proceeded to shoot 20 images using the 20 second self-timer to help eliminate camera shake. I was very excited to be shooting at such a massive magnification. The whole moon wouldn't even fit into my view-finder!

When viewed full screen, these images were covered with noise & tiny dust specs. There are lots of existing tools to remove dust, but I had 20 images, and thousands of spots... I really needed a way to complete the photo without clicking on each and every spot by hand. Also, removing these spots would reduce image detail and I wanted to preserve as much detail as possible.

I used Photoshop's "photo-merge" file-automation to open and align all 2o images onto one digital canvas. I used Photoshop's "dust and scratches" filter on each of the 20 image layers. I adjusted the tool to hide 90% of the specs that I saw at 100% zoom, but of course the tool cannot know what was obscured by each spot. All these dust spots just get averaged out of the image. I figured that since I had moved the camera before each shot, it was unlikely that any pixel of the moon was "dusted" in every shot. I just needed to reveal the "non-dusted" pixels...



Finally I selected the image mask for each layer, painted and blended the layer opacity using black and white paint at 30% flow. I used black paint to hide the defects & edges of each photo, and white paint to reveal 30% of each photo's detail. The details that appeared in the same place in every photo became clearer and clearer, and the noise that only appeared in a place for a single photo faded away.