Celestial hemisphere:  Northern  ·  Constellation: Cepheus (Cep)  ·  Contains:  HD212955  ·  HD213021  ·  HD214710  ·  HD215038  ·  LBN 558  ·  LDN 1251
LDN 1251 (The Rotten Fish Nebula), Michael Southam
LDN 1251 (The Rotten Fish Nebula), Michael Southam

LDN 1251 (The Rotten Fish Nebula)

LDN 1251 (The Rotten Fish Nebula), Michael Southam
LDN 1251 (The Rotten Fish Nebula), Michael Southam

LDN 1251 (The Rotten Fish Nebula)

Equipment

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Acquisition details

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Description

The Target
LDN 1251 (The Rotten Fish Nebula) is a star forming molecular cloud of dark and reflection nebula in the constellation Cepheus. At around 1,000 light years away, LDN 1251 is relatively close to our solar system. I find nebula far more satisfying to image than galaxies so I usually avoid imaging galaxies. This time though, 3 galaxies snuck into the field when I wasn't looking. The first is UGC 12160 located center left of the image just infront of the fish's mouth. This 15th magnitude Spiral Galaxy is 84 million light years from our solar system, has a diamiter of 32,020 light years and is receding from us at around 1,554 km per second or 0.5% of the speed of light. The second is spiral galaxy is PGC 166755 located above the image center and just above the base of the fish's tail. This is also a 15th magnitude spiral galaxy and is around 103 million light years from our solar sysyem. PGC 166755 has a diamiter of 37,828 light years and is receding from us at around 2,449 km per second or 0.8% of light speed. The third is spiral galaxy is WISEA J222834.94+750407.2 which is located just below the base of the tail and has a visual magnitude of 18.5. The galaxy is around 438,419,403 light years from our solar system, has a diamiter of around 115,752 light years and is receding from us at around 9,114 km per second or 3% of the light speed. Big thank you to Phil Harrington for finging it's identity.

Image Planning and Capture
As with most targets I image from Cherry Spring, LDN 1251 was chosen several weeks ahead of my visit to deepest darkest Pennsylvania. I devoted the trip to imaging rarely imaged dark nebula and LDN 1251 was chosen for is high position in the sky for the entirity of the night. The lowest the nebula got during night hours was around 45 degrees above the horizon meaning that I would get good quality data for the entire night. I always write an APT imaging script well in advance of the trip and this target was no exception. What was different was that neither Sky Safari nor Stellarium, my go to imaging frame positioning software, had a photographic representation of the nebula so all I had to work with was labels and a general circle where the nebula was located. This is entirely insufficient when your camera has a rectangular field of view that has to be aligned with the subject. What I did to get the correct field rotation was to superimpose a image of the nebula I found online, with a screen shot from Stallarium. From this I was able to determine that the optimum field rotation was 80 degrees clockwise from horizontal. I also used this superimposed image to pick the optimum center point for the APT imaging script to slew to. Armed with a script that refucuses every hour, all I needed was a clear sky and we were thankfully blessed with 3 great nights on the trip. The second night was entirely devoted to imaging LDN 1251. 

Image Processing
After a conversation with 2 fellow astroimagers at Cherry Springs, it became apparent that I may be doing my data a diservice not using Russell Croman's tools. I decided to see what I was missing and this is the first time RCs tools have been a part of my workflow. NoiseXterminator was applied pre stretch. BlurXterminator and StarXterminator post stretch in PI. The nebula and star images were then overlayed in PhotoShop and worked on seperatly. StarShrink was applied to the star layer which was blended with the nebula layer.

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