Lizard Head Nebula

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September 6, 2023 

I call this structure the Lizard Head Nebula. I gave it this nickname after Gail pointed it out in a wide-field image of the North America Nebula region in Cygnus, tucked in to the left of the Pelican’s beak. It has no catalogue number that I am aware of. The dominant colour in this image comes mainly from hydrogen emissions, although I included some oxygen-filtered data.  Like most of the other nebulosity in the region, this structure lies about 1,600 light years away.

Tekkies:
Acquisition, focusing, and control of Paramount MX mount with N.I.N.A., TheSkyX and PHD2. Primalucelab low-profile 2″ Esatto focuser and ARCO rotator. Equipment control with PrimaLuce Labs Eagle 4 Pro. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Average transparency and seeing. Data acquired on the night of September 5, 2023 under a waning gibbous Moon.

Celestron 14″ F/11 EDGE HD telescope at f/11 (3,912 mm focal length)  and QHY600M camera binned 2×2 with Optolong filters.

12x5m Red = 1hr00m
12x5m Green = 1hr00m
12x5m Blue = 1hr00m
16x5m Ha = 1hr20m
16x5m O3 = 1hr20m

Total: 5hr40m

Image scale 0.4 arcsec per pixel
 
Finder Chart: 
  
 
 
Data Reduction and Linear Processing

Preprocessing: The WeightedBatchPreProcessing script was used to perform calibration, cosmetic correction, weighting, registration, local normalization and integration of all frames.

Stars master: A master to use for the stars was made from the Red, Green and Blue masters using ChannelCombination in RGB mode. This was used only for stars.

Nebula master: A nebula master was made from the Ha and O3 masters using ChannelCombination in RGB mode, with Ha assigned to red and O3 assigned to green and blue.

Gradient Removal: DynamicBackgroundExtraction was applied to the RGB and HOO masters.

Colour Calibration:  ColorCalibration was used to calibrate the RGB master. SPCC in narrowband mode was applied to the HOO master with Photon Flux selected as the white reference.

Deconvolution: BlurXterminator was applied to the HOO master with Automatic psf , and star sharpening set to 0.10 with “Correct First” selected. 

Linear Noise Reduction: NoiseXterminator was applied to the HOO master with settings Amount=0.9 and Detail=0.35

Star Removal:  StarXterminator was used to remove the stars from the HOO and RGB masters, with default settings.

Stretching:  HistogramTransformation was applied to the HOO master and the RGB stars-only image to make pleasing images. Approximate background level after stretch was 0.10 for HOO and 0.02 for the RGB stars-only image.

Nonlinear Processing

Nonlinear Noise Reduction: NoiseXterminator was used to reduce noise in the background areas of the HOO image with settings Amount=0.9 and Detail=0.2

Re-stretch: HistogramTransformation was used to boost contrast by moving the dark point to the toe of the histogram and slightly decreasing the mid-point slider.

Contrast Enhancement: LocalHistogramEqualization was applied three times using a mask to select the brighter regions of the nebula.  A Contrast Limit of 1.5 and 1 iteration was used for each LHE application (scale 20, strength 0.35; scale 50, strength 0.25; scale 100, strength 0.2).

Sharpening: The same mask was used for sharpening with MultiscaleMedianTransform (Layers 1 – 5 with strengths of 0.01, 0.03, 0.05, 0.03, and 0.01, respectively). 

Stars-only steps: MorphologicalTransformation was used in Morphological Selection mode to shrink the stars through a mask made by extracting the Luminance from the stars-only image. CurvesTransformation was used to add saturation to the stars. 

Star Restoration: PixelMath expression combine(starless, stars, op_screen())  was used to combine the starless HOO with the stars-only RGB image. 

Final Steps: Background, nebula and star brightness, contrast, hue, and saturation were adjusted in several iterations using CurvesTransformation with masks as required. ICCProfileTransformation (sRGB IEC61966-2.1; Relative Colorimetric with black point compensation) was applied prior to saving as a jpg.  The finder chart was made using the FindingChart process.