Thursday, April 11, 2013

Out of This World Images

Oh, you thought I was talking about cats? No, when I say "out of this world", I mean it literally.

Through the Hubble Legacy program, NASA makes available the raw data captured by one of human kinds greatest achievements. (Well, I think the Hubble Space Telescope is one of our greatest achievements anyway.)

Unfortunately, you won't find JPEG files on the site, but rather a somewhat exotic format called "fits". I'll spare you the details on what exactly a .fits file is, but suffice it to say, it stores a lot of information. Just one channel of the image of galaxy M51, the galaxy used as an example in this article, is almost three hundred megabytes.

Here, I want to take a brief look at working with these images, and how you can create original spacescapes with real data. It's a great way to spruce up any space themed design, plus, you get the geek cred that comes with being able to say you've messed with the same raw data as NASA scientists.

If you'd like to follow along, head on over to the Hubble Legacy Archive, and download an image of your choice. I recommend looking for galaxy M51, because it's easy to find some very high quality images.

You'll also need software appropriate for handling .fits files. You'll need to research what is good for your platform, I'm a Linux user, so I'll be using ImageMagick. Now, some common programs such as GIMP can actually open the .fits files directly, but they can't handle the ultra-high bit depth of the files. I recommend ImageMagick because it properly supports arbitrary bit depth file operations. (Yes, arbitrary bit depth.)

When you first open the .fits file, it is likely to appear black. That's OK, it's just because there is very low light data. The sensor on the Hubble is designed to be sensitive enough to pick up light from distant stars, and also robust enough to view much nearer objects like, say, the sun.

In ImageMagick, I use the Stretch Contrast function to fix the exposure into something that makes visual sense. Once you're happy with the exposure, save the image out to a file.

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