LDN 1251, the Anglerfish Nebula, a 2-Panel Mosaic

LDN 1251, in Lynd's Catalog of Dark Nebulae, is a dense star forming region located in the constellation Cepheus. Together it and other objects combine to form the Cepheus Flare, a large molecular cloud above the Milky Way. Many objects are visible in this image including the dust of LDN 1251, LDN 1243, and a few galaxies including PGC166755 and PGC69472.

 

This image is a 2-panel mosaic taken over 10 nights, with approximately 19 hours of exposure time per panel.

 

- Location: Remote Observatory (Bortle 1, SQM 21.99) near Fort Davis, TX

- Total Exposure Time: 38.75 Hours

 

Equipment:

- Scope: Esprit 100ED w/ 1x Flattener

- Imaging Camera: QHY 268M

- Filters: Chroma LRGB (36mm)

- Mount: Astro Physics Mach1GTO

- Guidescope: SVBony 50mm Guidescope

- Guide camera: ASI 120mm mini

- Focuser: Moonlite Nitecrawler WR35

- Accessories: Pegasus Ultimate Powerbox v2, QHY Polemaster, Optec Alnitak Flip Flat

 

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Software:

- N.I.N.A for image acquisition, platesolving, and framing

- PHD2 for guiding

- PixInsight for processing

 

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Acquisition (Total between both panels):

- L: 380 x 3m

- R: 132 x 3m

- G: 131 x 3m

- B: 132 x 3m

- All images at Gain 56, Offset 25 (Readout mode 1) and -5C sensor temperature

- 20 flats per filter

- Master Dark, Flat & Bias from Library

- Nights: 6/23-6/27, 6/30, 7/1-7/3/22

 

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Processing:

 

- BatchPreprocessing for all calibration

- ImageIntegration with PSFSignalWeights for integration of all masters

 

Combining panels for each master:

- DynamicCrop on each panel

- DynamicBackgroundExtraction on each panel

- ImageSolver to platesolve panels

- MosaicByCoordinates script to create mosaic templates

- PhotometricMosaic script to create 2-panel LRGB masters

 

RGB Processing (apply to each master):

- FastRotation 90 degrees

- DynamicCrop

- DynamicBackgroundExtraction

- NoiseXterminator for linear NR

- StarAlign B and G to R

- ChannelCombination to combine into linear RGB image

- DynamicBackgroundExtraction to remove color gradients

- STF for stretch to non-linear

- CurvesTransformation to balance color

 

Luminance Processing:

- FastRotation 90 degrees

- DynamicCrop

- DynamicBackgroundExtraction

- NoiseXterminator for linear NR

- GeneralizedHyperbolicStretch for initial stretch

- HistogramTransformation x2 for further stretch

- CurvesTransformation on starless copy to increase nebulosity

- PixelMath to combine pushed starless and original via: (1- (1-$T) * (1-star)*F)+($T*~F) where F=0.3

- CurvesTransformation for contrast

 

Combine RGB and Luminance:

- StarAlign RGB to Luminance

- LRGBCombination with RGB channel weights set to 0.9, chrominance NR enabled, and saturation boost

- SCNR green @ 0.2

 

Further Processing:

- CurvesTransformation for contrast

- NoiseXterminator for slight nonlinear NR @ 0.2

- Starnet2 to create starmask

- MorphologicalTransformation for slight star reduction

- ColorSaturation to saturate brown dust

- CurvesTransformation for contrast

- DynamicCrop to remove edges

 

Created Annotated Version:

- Duplicate final image and StarAlign to initial linear Luminance

- ImageSolver script on luminance

- Transfer FITSHeader from solved luminance to staraligned final image

- AnnotateImage script to label objects

- DynamicCrop to remove edges

- IntegerResample to downsample 2x

- Save as PNG

Done