Beginning Astrophotography: Saturn

Recording a video of Saturn through a 25 mm Plössl eyepiece.
Recording a video of Saturn through a 25 mm Plössl eyepiece.

I have waited a long time since I first saw Saturn two years ago through a telescope to see it again and properly photograph it. For a number of reasons, it took until last night before I finally got the chance.

By changing a few things, I improved my Saturn photos considerably over my previous Jupiter ones.

  • I realized I needed to collimate my telescope. This means that the secondary mirror had gotten very subtly out of alignment with the primary mirror, and I had to use a tiny screwdriver to move it back into alignment. Once I did this, I found I was able to focus on things better. This also meant that I could use higher magnification.
  • I took advantage of the more precise focus by putting a Plössl eyepiece into one of my camera adapters. This allowed me to magnify what it saw and gather more detail.
  • Finally, I’ve been searching out better software workflows and practicing with the software I have to get better at image stacking and polish the results. I’ve mostly replaced PIPP and RegiStax from my Jupiter post.

Example video clip

With these improvements, last night, I took a few longer videos at different focal lengths and with different camera settings. Below is a short ten-second clip as an example of what I captured. It was taken with my typical Sony α6300 connected to my telescope with an adapter through a 25 mm Plössl eyepiece. The video is at 4K resolution.

Software

The core activity of the software I’ve used for improving the images I’ve taken is stacking. What and how I stack ultimately determines which software I use.

I had already been frustrated by RegiStax due to its complexity, instability, and inflexibility. From searching online and reading others’ experiences, they often stacked in another program and used RegiStax for its wavelet features only. The most popular program for stacking appeared to be one called AutoStakkert!.

Once I replaced RegiStax, the rest of my workflow changed too. I began practicing with AutoStakkert and found that it minimized my need to use PIPP. I could essentially load a video directly into AutoStakkert without preprocessing it as much.

From there, the program itself was (relatively) more straightforward to use. There are detailed guides for its use available online, so I won’t recapitulate its usage here—I’m still learning it myself.

Screenshot of AutoStakkert! after use on a video of Saturn showing its features, parameters, and timings.
Screenshot of AutoStakkert! after use on a video of Saturn showing its features, parameters, and timings.

Once it’s finished with the source video, it has taken all the individual frames and combined them into a single image that looks, actually, not that useful, like a ghostly blurry image.

Stacked but unmodified image of Saturn
Stacked but unmodified image of Saturn, before applying wavelets, sharping, histogram stretching, rotation, etc.

AutoStakkert! doesn’t replace all of RegiStax’s features, such as the wavelet filters, so you’re left to do that on your own. I could load this into RegiStax to finish up then, but I found another piece of software called Astra Image that’s dramatically simpler and more powerful to use. This is the first piece of software I’ve mentioned so far that actually has cost money. It has a “Wavelet Sharpening” feature that brings the details right back out. In the very same program, I can apply additional sharpening, denoising, contrast, saturation, and  flipping over the vertical and horizontal axis.

After all that, I get the final image.

Final image of Saturn formed by stacking 40% of the frames of approximately two minutes of video.
Final image of Saturn formed by stacking 40% of the frames of approximately two minutes of video.