Sadr Widefield (RGB)

Sadr Widefield (RGB)

This is the Sadr widefield region (the bright star in the center of the image). It is a large and nebulous region in the constellation of Cygnus. Cygnus is a constellation directly on the plane of the milky way, which is strongly visible by the sheer amount of stars on that image. Sadr itself is the “center” of the Swan and a part of the Northern Cross. It is approximately 1800 light years away from earth.

The brightness of Sadr itself would make you think that it is a very large star. And it indeed is. It is one of the most prominently visible stars in the northern hemisphere with an apparent magnitude of around 2.23. It is suspected to be around 12 times of our suns mass and around 150 times radius as well. Sadr is around 12 million years old by current estimations.

Surrounding Sadr is the Sadr nebulous region, or also known as IC 1318. It is a diffuse emission nebula primarily consisting of hydrogen alpha emissions. It also features several dark nebulae around it. With the large field of view other nebulae like the Crescent Nebula and several open star clusters are visible on that image as well. Check out the Annotated Image below to have an annotation of all DSO in that area.

Technical Details

First test with my new Samyang 135mm f/2 lens! Exciting! This image has an extremely low total integration time, barely over 60 minutes total. I am honestly strongly surprised how well that lens keeps up widely open at f/2. Sure, some stars show some elongation, especially on the left side of the image, but hell, that is one flat star field.

From what I can tell is that my sensor apparently has some minor tilt, which I might have to take care for, but it is not a priority for me right now. Everything considered I am very pleased with this image.

This image was acquired on the Lunar Eclipse night, where I enjoyed the astro dark provided by the eclipse and managed to squeeze in an hour of integration during the time the sun went down and the eclipse was over. At least the eclipse was good for something, heh.

Acquisition Details

Shot with Nikon D5100 on Samyang 135mm f/2 at f/2

Date: 2018-07-27
D5100 RGB: 63×60s 1×1 binned

Postprocessing Details

RGB (D5100)

  • Dynamic Crop
  • Dynamic Background Extraction
  • PhotometricColorCalibration (G2V Star White Reference)
  • TGVDenoise and MMT by Jon Ristas method
  • ArcSinhStretch (100)
  • HistogramTransformation
  • SCNR (Green)
  • MorphologicalTransformation (Star Size Reduction)
  • LocalHistogramEqualization (Nebulosity)
  • CurvesTransformation (Small Star Saturation)
  • CurvesTransformation (Large Star Saturation)
  • CurvesTransformation (Nebulosity Saturation)
  • BackgroundEnhanceScript
  • HistogramTransformation (Black point to 0)
  • CurvesTransformation (Orange hue shift into red on Nebulosity)
  • CurvesTransformation (Red hue shift into pink on Nebulosity)
  •  AutomaticBackgroundExtraction (Get rid of blue corners)
  • CurvesTransformation (Nebulosity Saturation)
  • Export as 16bit TIF

Annotated Image

Sadr Widefield (RGB, Annotated)

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