Thor’s Helmet (NGC 2359) is an emission nebula in Canis Major. At first glance one might think it is a planetary nebula, but it is a Wolf-Rayet bubble like the Crescent and Bubble nebulae. These are bubbles created by more recent but faster stellar winds catching up to and colliding with older but slower stellar winds. In this case, it is thought that there are interactions with other gas in the region and that accounts for the filamentary structures radiating away rom the main bubble.

The nebula is nearly 12,000 light years away and spans approximately 30 light years across. It’s one of the more spectacular nebulae in the night sky with lots of detail and structure.

This is in the Foraxx palette. This is a dynamic combination of data meaning that individual color channels end up being a complicated blend of the raw filter data. It can produce an image with a more pleasing starting point than the traditional SHO combination and although I’m often not a fan, in this case it did the trick as the other tricolor combinations I looked at weren’t as satisfying. You can find more info about the palette and PixInsight script here: https://www.astroworldcreations.com/news/new-foraxx-script-for-pixinsight and https://thecoldestnights.com/2020/06/pixinsight-dynamic-narrowband-combinations-with-pixelmath/.

This is 17h 10m of narrowband data. For all the technical details, see astrobin.