The Medusa Nebula

Here’s the latest image I’m adding to my collection. I took this over two nights in late January, took some time getting around to post processing it. The Medusa nebula is fairly faint and small as nebula go, so I went with my longer focal length setup. I was hoping one night would be enough, but it clearly wasn’t, and when the weather cleared I managed to get second night in.

There were a few hiccups in the post processing. First off, the Medusa nebula isn’t in the multi-scale gradient correction database, so that process failed. No worries, GraXpert is a good backup.

The second hiccup was a little more PixInsight specific. I tend to just throw all my subs to the stacking process without really culling bad subs. Usually that works fine. This time it didn’t. The weather was spotty, mix of scattered clouds, thin clouds, and clear skies. On some subs guiding had failed, others had cloud obscuration, and others had both. It seems the wide range of sub quality had opened up PixInsight’s statistical thresholds too much, and it wasn’t able to automatically cull bad subs. So I manually culled about 10 really terrible subs from the stack and retried. This time the Weighted Batch Preprocessing tossed another 10 subs and the stack was much better.

From there on it was an uneventful post-processing following my standard OSC Nebula workflow.