AstroBinAstroBin
Celestial hemisphere:  Southern  ·  Constellation: Canis Major (CMa)  ·  Contains:  16 CMa)  ·  The star Udra (ο1 CMa
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Sh2-308, Dolphin Head Nebula, Doug Summers
Sh2-308, Dolphin Head Nebula
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Sh2-308, Dolphin Head Nebula

Getting plate-solving status, please wait...
Sh2-308, Dolphin Head Nebula, Doug Summers
Sh2-308, Dolphin Head Nebula
Powered byPixInsight

Sh2-308, Dolphin Head Nebula

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Description

At ~5000 light-years distance, a giant bubble of expanding ionized hydrogen from an ultra-hot Wolf-Rayet star (EZ Canis Majoris, the bright blue star near the center of the bubble) forms what looks like a dolphin's head.   The winds from EZ Canis Majoris blow at an extreme rate; estimated at 3.8 million miles/hour!    The nebula is thought to be 70K years old with a diameter of 60 light years.   At some point in the distant future, this Wolf-Rayet star will exhaust its remaining fuel and go supernova.

This image is one of the most unique objects I've imaged to date.   What I find interesting about this HII region is that it images mostly green in the IMX183 sensor.   I'm not sure why that is since it is  ionized Hydrogen.  I would have expected more of a red color.   Most people seem to favor a false blue color for the nebula, but I've only slightly shifted blue and have retained much of the green hue that the sensor indicates. 

This nebula, like other nebula containing particularly bright stars, simultaneously shows both the strength of the RASA11 and its primary weakness.   The bright orange star at the top of the nebula is Udra (16 CMa).  This magnitude 3.8 star overwhelms it's region of the image with diffracted light.  In fact, all the brightest stars in the image have a similar effect in their regions.   I had to run 2 iterations of star reduction (beyond the BlurXTerminator deconvolution which already reduces star PSFs), and use curves reduction to beat down the brightest stars in the image.   Some if this is my own fault; I need to do a better job of circularizing my cable routing to the prime focus camera (which I'll do asap).  That should reduce but not fully eliminate star diffraction spikes.  It won't however eliminate the full aperture halos that are visible around extremely bright stars such as Udra.

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Sh2-308, Dolphin Head Nebula, Doug Summers

In these public groups

Celestron RASA
The OSC Club (One Shot Camera)

In these collections

Bright/Dark Nebulae
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