Elephant Trunk Nebula in natural colour

[MarkS]

My first image for quite a while. This is IC1396 shot with an unmodified Canon EOS R and processed with careful attention to preserving the natural colour:



Larger version is on Astrobin: https://www.astrobin.com/tc1c37

Acquisition details are the following:

• Unmodified Canon EOS R on Takahashi Epsilon 180ED and Skywatcher EQ6 Pro mount
• 150 x 2min dithered exposures at ISO 1600
• SQM sky quality reading averaged 20.75 (i.e. Bortle 4)

Natural colour processing in PixInsight with the following main steps:

• Calibration with flats, bias and optimised (i.e. scaled) darks before CFA drizzle stacking with x2 scale
• Noise reduction followed by 2x2 binning
• Apply daylight white balance
• Apply CCM (colour correction matrix) from camera colour space to linear sRGB (CCM sourced from DxOLab)
• More noise reduction
• DBE (DynamicBackgroundExtraction) to subtract light pollution
• ArcsinhStretch
• Slight CurvesTransformation to improve contrast
• Apply the sRGB tone response curve

Note that the non-linear steps (ArcsinhStretch and sRGB gamma curve) were the final 2 steps in processing. This is the key to maintaining good colour fidelity throughout the entire dynamic range. Photoshop was used for the noise reduction (I find it easier!) but all other steps were performed in PixInsight.

Question: What is the tiny blueish-green irregular nebulosity diagonally upwards and right of the garnet star?

Mark

[Carole]

Good to see you imaging again Mark, you haven't lost your touch, and this is a great image. 

Not used to seeing this target in broadband, most images of this target are in NB but it is good to see it in natural colours, particularly the garnet star.

What is the tiny blueish-green irregular nebulosity diagonally upwards and right of the garnet star?

, that is fascinating, and presume it is a nebula too small to be catalogued.  Might be worth posting the question on Astrobin as there are over 10,000 members on there, maybe someone might be able to answer that question, it certainly doesn;t come up in the plate solving.

Carole

[MarkS]

that is fascinating, and presume it is a nebula too small to be catalogued. 

I found the answer. It is a planetary nebula variously denoted by "PN G100.4+04.6", "IRAS 21394+5844", "PK 100+04.1".  Here on Simbad: http://simbad.u-strasbg.fr/simbad/sim-id?Ident=PN+G100.4%2B04.6

Clearly it's a strong OIII emitter.

Mark

[Carole]

Well done.  Did you get it by putting in the co-ordinates?

Carole

[MarkS]

Did you get it by putting in the co-ordinates?

No, I eventually got it from PixInsight's AnnotateImage script.  It labeled the object as "PK 100+04.1"

[The Thing]

I like this one Mark, it looks 'real' as if we had more sensitive eyes.

You can get CCM data for consumer cameras from DXoMark, is there an equivalent for sensors e.g. the IMX294?

[MarkS]

You can get CCM data for consumer cameras from DXoMark, is there an equivalent for sensors e.g. the IMX294?

Unfortunately not. But in theory it would be possible to compute one given a raw file of a ColorChecker illuminated by sunlight.