Unblurred Utah Sky

When you sacrifice sleep you can accomplish great things (for a brief period of time). Finally, after about a year of work, I have come up with a workflow to automatically enhance my stellar photography.

This picture is worth zooming in on. Some places look like they could be galaxies but unfortunately are nothing more than noise caused by over saturation from bright stars.
This picture is worth zooming in on. Some places look like they could be galaxies but unfortunately are nothing more than noise caused by over saturation from bright stars.

The image above was produced with my collection of 518 source images taken last year. I’m not sure how much better I will be able to make it (ignoring the fact that I haven’t yet corrected for the coma-distortion in the corners). The reconstruction was a fun process which I will write about later, but the following animation demonstrates how the various stages look.

Moving from raw imagery to reconstructed imagery. Notice how the two overlapping stars near the center of the image separate towards the end of the process.
Moving from raw imagery to reconstructed imagery. Notice how the two overlapping stars near the center of the image separate towards the end of the process.

This reconstruction is mainly a combination of two algorithms: the first aligns and sums the individual frames, reducing the noise and increasing the SNR (signal-to-noise ratio); the second takes an inferred PSF (point-spread function) and performs an iterative deconvolution to estimate the original unburied scene.

The biggest surprise during this project was discovering that the pictures I took were out of focus. In the first frame of the animation, you can see that each star looks like a small donut – a ring around a dark center. This is most likely caused by the fact that the point where all the light should have landed on the camera sensor was actually behind or in front of where it needed to be. Thus, every spot in one of those tiny rings represents the same physical spot in space.

Luckily, by using a bit of math and lots of processing power I was able to remove that out-of-focus blur and recover the sharper stars, now appearing as points. The image produced is literally a higher-resolution image than is physically possible for the camera to capture. It’s only by the application of algorithms like these that we can cheat reality to admire the treasures hidden inside.

Next step? Apply this process to some of my other more-recent astrophotography, then try and capture a portion of space through a telescope and capture galactic arms.

Sex Tractor Preview

No, it’s not a racy post. It’s a play on words some funny programmer chose for the name of this StarExtractor. Actually, it’s called sextractor without the space, but I digress.

It may not look that impressive now, but it carries massive implications.
It may not look that impressive now, but it carries massive implications.

This represents a big step forward in my pursuit of a clear shot of the night sky. The process that I have worked out requires automatic alignment of each shot from my nocturnal photo-shoots, but the algorithms I have been using keep failing. My suspicion is that they fail because they are looking for features and the stars are just a bunch of points – featureless.

This, however, changes everything. This is a line drawn among the fifty brightest stars in the central area of the image and I was able to produce it automatically with the help of sextractor, which identified and classified the stars in the image. These lines will hopefully be enough of a set of features for the other algorithms to match.

Onward and forward!