I actually didn’t plan to image this object, because from my latitude it sits very low near the horizon, buried in light pollution and turbulent air. However, it was nominated for the February 2018 deepsky imaging challenge on CloudyNights.com, so I gave it a shot.
Man, this was indeed a difficult nebula! The individual sub-exposures barely showed anything, even with narrowband filters.
Thor’s Helmet (NGC 2359) is a nebula formed around a Wolf-Rayet star. These extremely luminous giant stars have depleted their hydrogen supply and are near the end of their lives, ready to go supernova. They are usually surrounded by a bubble of gas and interstellar material, lit up by strong solar winds from the central star.
The bubble around WR7 (the bright star in the center of the nebula) has an estimated size of 30 light-years, while the WR star itself is calculated to be almost 300 000 times brighter than our own sun.
Processing:
I created tone maps from both channels, combined them in a super luminance and then added the OIII stars. Copies of the tone maps were treated with strong noise reduction and combined as HOO for color.
Date: 22 February 2018
Telescope: Teleskop-Service 80/480 triplet with 2″ TS 0.79X reducer/flattener and Baader 2″ UV/IR filter
Camera: ZWO ASI1600MM-C with EFW-8 and ZWO 31mm filters
Mount: Skywatcher EQ5 Pro
Exposure: 1.6 hours
Ha 7 nm: 25 x 120 sec (gain: 200, bin 1×1, -15C)
OIII 7 nm: 23 x 120 sec (gain: 200, bin 1×1, -15C)
Software: APT, PHD2, EQMOD, PixInsight
Astro Virus 
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