Jellyfish Nebula (IC443)

By Anton Winter

The Jellyfish Nebula, having an official designation of IC443, is a supernova remnant about 5,000 lightyears from Earth that occurred between 3,000 and 30,000 years ago.

I captured this image from my light-polluted Bortle 6 backyard in San Ramon, California.


  • Telescope: SkyWatcher ESPRIT 100ED
  • Imaging Camera: QHY-268C
  • Guide Scope: PrimaLuceLab 60mm
  • Guide Camera: ZWO ASI2900MM
  • Mount: SkyWatcher EQ66-R Pro
  • Electronic Focuser: PrimaLuceLabs SESTO SENSO 2
  • Filter: Optolong L-Extreme dual-band astronomy narrow-band filter (Hb, Ha, and OIII)
  • Capturing Software: N.I.N.A.

How much data did I capture?

Exposure Time: 2.8 hours

What about image processing?

There is still a lot of trial and error when processing this data captured with the Optolong L-eXtreme dual-band filter that only passes Ha and OIII emission lines. I am producing a HOO image where Red, Green, and Blue are mapped to Ha, OIII, and OIII, respectively, hence the ‘HOO’ color palette.

A challenging part of processing this image, which I failed to solve, was the large halos around the two bright stars close to this nebula. The Optolong L-eXtreme filter I used causes these imaging artifacts due to the light from these very bright stars bouncing off the astrophotography camera sensors glass, to the filter, and back to the sensor again. I tried various ways of removing this but was relatively unsuccessful. Something I need to work on in future imaging sessions.