Thor's Helmet, NGC 2359

Thor's Helmet, NGC 2359, is an emission nebula in the constellation Canis Major. A semispherical bubble formed on the right side of the nebula. At its center is a Wolf-Rayet star, WR7, in the later stages of its life. The solar wind from the Wolf-Rayet star formed the bubble. The nebula is composed of ionized gasses excited by the radiation from the Wolf-Rayet star. (NSF NOIRLab)

This image is a narrowband image. Ionized gases in this nebula produce three prominent emissions: Hydrogen Alpha (656.3 nm), Sulfur II (672 nm) and Oxygen III (500.7 nm).

A formula is used to assign pixel values to RGB channels. The purpose is to more closely emulate the classic Hubble Palette. The specific palette I used is the Foraxx Palette.

(PixInsight Forum)

The color mapping, for this image, is as follows:

Red: (OIII^~OIII) * SII + ~(OIII^~OIII) * Ha

Green: ((OIII*Ha)^~(OIII*Ha))*Ha + ~((OIII*Ha)^~(OIII*Ha))*OIII

Blue: OIII

Bottom line, this mapping communicates the composition of different regions in the nebula. It does not represent the way the nebula appears to our eyes.

Image processed by Andrew Macica, original data from Telescope Live.

Imaging Details:

Observatory: Rio Hurtado Valley, Chile

Telescope: Planewave CDK24

Aperture: 610 mm (24 inches), f/6.5

Focal Length: 3962 mm

Camera: QHY 600M Pro CMOS

Filters: Ha, SII, OIII

Total Exposure: 9 hours 15 min.

Image Processing:

PixInsight 1.8.9-3 Ripley (x64);

BlurXTerminator, NoiseXTerminator, StarXTerminator (RC Astro);

Python 3.9;

Adobe Photoshop 25.12.1;

Adobe Lightroom Classic 14.2

Instruction on PixInsight from Adam Block Studios.