Six moons and a planet

In the race to take best resolution images of Jupiter and Saturn at highest powers and frame rates, the moons often get neglected. Personally, I do like to see entire systems with their ever-changing view.

Of course, the moons are fainter than the planet so usually the planet will be terribly overexposed when the moons are imaged. At the cost of photometric unscientificness, this can be overcome by merging multiple exposure times in a single image. Here is one of Saturn that shows six of its moons, including faint Hyperion at around 15th magnitude.

And because that is really just a lot of dots without context, here is an annotated version

The process I use is to take a few short exposure frames as for normal planetary images, then one or two longer exposures, then repeat. Each of these frame sets is combined into a meta-frame by some scripting fu that attempts to pull signal from the longer exposures into the dark areas of the shorter exposures. The composite frames can then be stacked as usual. I made a similar one in March for Jupiter

For that one I actually took a gazillion frames over three hours in the hope of making a video out of it once I fully automate the compositing process. Unfortunately I seem to be building up a bit of an image processing backlog. Even now, while I’m trying to reduce the pile, the sky turned clear and the telescope is collecting data outside – argh!