Astrophotography Books

Steve here. These are the books I'm using to learn about astrophotography (in addition to watching YouTube videos):

• The Deep-sky Imaging Primer, Third Edition, by Charles Bracken.
  
• A Deep Sky Astrophotography Primer: Creating Stunning Images Is Easier Than You Think!, by Michael O'Brien.
  

It's a two-stage process: imaging, i.e. taking picture; and image processing. The real technological revolution is that the image processing means even fairly modest equipment can capture suitable images that eventually produce mind-boggling results.

The secret is "image stacking." The old method of astrophotography was to take long-duration exposures of minutes or even hours, accumulating photons on the film. One hiccup during the session could ruin the image.

The new method is to take numerous short-duration exposures (less than a minute), then use the software to pick out the best ones and accumulate the photons in the digital "stack" of data. Both methods require precise tracking of celestial objects using a tracking mount, but now hiccups just mean the bad exposures get thrown out.

The software handles lining up the data between photos. It's really quite amazing. Also, most of it is free.

In the process, it improves the signal-to-noise ratio, i.e. increasing the good stuff in the image (the signal) while filtering out the static (the noise, the randomness in the electrical signals in the image sensor). That makes the lights lighter and the dark darker.

The other thing it does is make the data visible to the human eye. We don't see in the same wavelengths that stars emit, but the digital imaging sensor does. The software remaps the wavelengths to those we can see, "stretching" the narrow band of emission light in the overall image histogram across the visible spectrum. The invisible becomes visible.

The result is spectacular images that look like you must have taken them from space.