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.

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.