NGC 2832 Galaxy Cluster

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April 5, 2023

Galaxy season continues, with a pretty galaxy cluster centred on NGC 2832, in the constellation Lynx. NGC 2832 is about 340 million light years away, and is a little larger than our own Milky Way galaxy. It makes a tight triplet with NGC 2830 and 2831. See the annotated image for catalogue numbers and locations of the many galaxies dotted throughout the field. 

Acquisition, focusing, and control of Paramount MX mount with N.I.N.A., TheSkyX; unguided.  Focus with Optec DirectSync motors and controller. Equipment control with PrimaLuce Labs Eagle 4 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Good transparency and seeing. Acquired March 14 – 19, 2023 under a moonless sky.

Sky-Watcher Esprit 150 f/7 refractor and QHY600M camera with Optolong UV/IR filter
Tak FSQ-106 @ f/5 (530mm), QHY-367C Pro One-shot colour, Optolong UV/IR filter 

61x5m Lum = 5hr05m
61x5m OSC = 5hr05m
Total: 10hr10m
Image scale 0.72 arcsec per pixel 
Finder Chart and Annotated Image: 


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, plus DrizzleIntegration for the OSC data (2x with ddrop shrink=0.9).

Alignment of Master Frames: The Drizzled OSC master was aligned to the Luminance master with StarAlignment. This yielded aligned Lum and Colour masters.

Gradient Removal: DynamicBackgroundExtraction was applied to both masters.

Colour Calibration:  SpecrophotometricColorCalibration was used to calibrate the OSC master.

Deconvolution: BlurXterminator was used on each master with a custom psf FWHM determined with the PSFImage script, and star sharpening set to 0.10 with “Correct First” selected.

Linear Noise Reduction: NoiseXterminator was applied to each image with settings Amount=0.9 and Detail=0.15

Stretching:  HistogramTransformation was applied to each image to make a pleasing yet bright image.

Nonlinear Processing
Luminance addition: LRGBCombination was applied to replace the lightness of the RGB image with the Luminance master.

Star Removal:  StarXterminator was used to remove the stars, with Unscreen selected

Nonlinear Noise Reduction: NoiseXterminator was used to reduce noise in the background areas of the image with settings Amount=0.9 and Detail=0.1 

Star Processing: The lightness was extracted from the stars-only image and used as a mask on that image. Curves was applied to boost saturation. The MorphogicalTransformation was applied to shrink the stars slightly (Morphological selection mode, Selection = 0.3, Amount 0.75, 3×3). 

Star Restoration: PixelMath expression combine(starless, stars, op_screen())  was used to combine the starless and stars-only images created with StarXterminator.

Final Steps: Background, galaxy and star brightness, contrast 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. Image was annotated with the AnnotateImage script. Finder chart was made using the FindingChart process.