Dolphin Nebula, sh-2-308

This is an image of the Dolphin Nebula, sh-2-308. This object is an HII Region, forming a bubble, and is located at the center of the constellation Canis Major.

The bubble is composed of ionized gas. A Wolf–Rayet star named EZ Canis Majoris is located at the center of the bubble. The star's radiation ionizes the gas, making the nebula visible. The solar wind from the Wolf–Rayet star produces the bubble-like structure. This star is in the brief, pre-supernova phase of its stellar evolution. (Sky & Telescope)

The nebula gets its name because the bubble forms the shape of a dolphin's head.

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 F. Macica, original data from Telescope Live.

Imaging Details:

Observatory: Heaven's Mirror Observatory, Yass, Australia

Telescope: Takahashi FSQ-106ED

Aperture: 106 mm (4.17 inches), f/3.6

Focal Length: 382 mm (with 0.73x focal reducer)

Camera: QHY 600M Pro CMOS

Filters: Ha, SII, OIII

Total Exposure: 8 hours 45 minutes

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.