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Astrophotography

The Ghost Fish Nebula
Jeffrey McClure

It's hard to know what to call this image. I should note that astronomers call it a "narrow band" image in that only three very narrow light frequencies are captured instead of the full visual spectrum of light. Excited sulfur, hydrogen, and oxygen atoms emit those three very narrow bands in the near vacuum of deep space when they have received more energy than they can handle and radiate photons at their respective frequencies, which we refer to as Sulfur II, Hydrogen-alpha, and Oxygen III. I have mapped the H-alpha to green, the S-II to red, and the O-III to blue for this image because we see the most detail in green since we have two green receptors for every red and blue receptor in our eyes. NASA uses it frequently for images captured by the Hubble Space Telescope; thus, we call it the "Hubble palette." The image is about 5.4 degrees wide and 3.5 degrees high, and north is up. As a point of reference, the Moon is about 1/3 of a degree in diameter, so this picture is a bit more than ten moons high and 16 full moons wide. In astronomical terms, the area covered is "BIG".


This particular bit of the sky is located in the constellation Cygnus (the Swan) just south and east of the bright star Sadr. Near the upper edge and halfway to the left side is the result of a more or less constantly exploding Wolf-Rayet star WR 136, known more commonly as the Crescent Nebula (NGC 6888) about 5,000 light years from us, a reasonably good distance to stay away from a continuously exploding red giant star about 6,000 times brighter than the sun, 21 times more massive, and about 5 times larger, not to mention the frequent explosions and that it will probably blow up as a supernova in the next couple of hundred years. The Crescent is blue because, in the process of all that blowing up, WR 136 is creating a lot of elemental oxygen, a good thing for those of us who like to breathe the stuff.

On the left (west), the bright little blob is prosaically named Sharpless 2-104 and is quite excited by the new birth of a small cluster of stars named collectively "Kronberger 74," only about two light-years across and about 5,740 light years away from us. In the lower right are a series of snake-like Bok nebulae (embryonic stars in danger of being blown away by their neighbors) named LBN 170, 174, and 182. In the middle of it all is a glowing mountain of hydrogen gas, the northwest edge of which looks a little like an eagle's head, affectionately known as LBN 187, so I will call it: "The Eagle's Head."


Of perhaps passing interest, the blue, slightly curved column of brightly glowing oxygen just to the left and down from the center, which to me looks a bit like a skeletal ghost fish trying to grab a bird flying by, seems to have no name and is being generally ignored by astronomers, so I will name it and the entire image "The Ghost Fish Nebula."

The data for this image was captured using a Takahashi FSQ-106 ED telescope with a QHY 600M camera belonging to Telescope Live, located in Oria, Almeria, Spain, high on a desert mountain where the air and skies are almost always cloud-free, dry, and clear. I then downloaded the data for processing here in Salado, TX, USA, where the sky is almost always cloudy when the moon is not full.

Jeffrey McClure

By the way, I used Pixinsight to process this monster. To keep the stars from getting out of control as I was stretching the image and digging out the details, I removed them and whittled down the smaller stars to keep them from obscuring the nebulae, then added them back in just before converting the image to non-linear.

Willie
Very cool, Jeff.

Willie

abrickhouse
I have never heard of the Ghost Fish nebula and I am not sure there is the slightest resemblance to a fish..

But its good processing and the Crescent looks great. You would think that they would run this in RGB with the clear skies there.

Aubrey
Jeffrey McClure
Well, Aubrey, I have a list of all the names and designated nebulae and it appears there is not one at that location despite or being so prominent in this image, and since I see it I will name it :). That area is far more interesting in the Hubble palette than in RGB, Thai is why I chose it. 


Jeffrey W. McClure
(254) 258-9203



Jeffrey McClure

Aubrey, First, here is a link to the nebula I referred to as "ghost fish": https:

https://www.astrobin.com/full/ixg5aj/0/


I think you can see the outline of a fish there.


In a bit of new information, I could only find a generalized name for the nebula, aprt of LBN 182, which referres to the entire OII nebula surrounding WR 134 as the "Almost Eye" nebula, and referrs to the entire bubble of OII around the Wolf-Rayette star.


I elected to work on this in narrow band because that object as well as much of the other interesting structure in the area is only visible using OIII, and simply appears to not be there in LRGB. For reference, here is a visual color image of nearly the same area: https://www.astrobin.com/full/edt7j5/0/


I am fascinated by the underlying structure of the nebulae and find it beautiful, so I commonly reduce the star halos to eliminate the bloom caused by light passing through Earth's asmosphere, revealing what I believe is a more realistic representation of the stars and eliminating their obscuration of the background nebulae.

Dick

I see a spooky looking fish staring at me. Very nice.

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