The Dolphin Nebula, also known as Sh2-308, is a fascinating celestial structure located approximately 4,500 light-years away. This nebula is shaped by the powerful stellar winds from its central star, a Wolf-Rayet star (EZ Canis Majoris, WR 6).
Wolf-Rayet stars are known for their massive size, intense radiation and fast winds, which sculpt the surrounding gas to form beautiful and complex nebulae.
In the case of the Dolphin Nebula, the interaction between the wind from the star and the surrounding material creates a bubble-like structure that resembles the shape of a dolphin.
Sh2-308 has a diameter of about 60 light-years, making it a relatively large but faint nebula.
Imaging the Dolphin Nebula from the latitude of my observatory (42 degrees) presents significant challenges due to its low position in the sky (DEC -23º 56’): Located in the southern constellation of Canis Major, the nebula never rises much above the southern horizon of Àger. This low altitude means that the light from the nebula has to pass through a larger portion of the Earth's atmosphere, which can cause atmospheric distortion, reduce image clarity, and increase the likelihood of light pollution affecting the observation. Because of these reasons I discarded to image it in the past.
But last year (2024) the astrophotographer Aleix Roig presented an extraordinary image of this nebula taken from a place not far south of my observatory and demonstrated that it was possible to image it properly from our latitudes. So I changed my mind (thank you very much, Aleix!!).
So during December 2024 and January 2025 I have been accumulating exposure with my dual setup: about 100 hours in total.
I decided to produce two images: one, a detail image of the nebula in narrowband (HOO palette, RGB stars) with TOA-150 (1.69 “/pixel) and a second one, a widefield in RGB at 3.49”/pixel.
Some processing notes (HOO image)
Regarding color, I have used SpectrophotometricColorCalibration in narrowband filters mode to have a starting point and a neutralized background, but later I have changed the color balance to my personal taste.
I found that in this image the use of BlurXTerminator, both in Correct Only and Normal mode has been absolutely mandatory 😅.
Regarding MultiScaleGradientCorrection, unfortunately there is still no coverage of this area in their databases. So I used the GradientCorrection tool (with Simplified Model, Automatic convergence and no Structure protection).
Some processing notes (RGB image)
The second image was taken with FSQ-106N and is a hybrid RGB image, with Ha added to the red channel and OIII added to the green and blue channels.
Note: on the FSQ I have my (very) old set of RGB Baader filters which unfortunately produce very unpleasant halos on the big stars.
Click on the images for full resolution versions, or go to the Gallery section for complete exposure details.
Image processing: Pixinsight.
Observatory automation and remote operation with Talon6.
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