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Contains:  Witch Head nebula, IC 2118, NGC 1752, The star ψEri
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Witch Head Nebula (IC 2118), 





    
        

            Andrew Klinger
Witch Head Nebula (IC 2118)

Witch Head Nebula (IC 2118)

Technical card

Resolution: 4460x3333

Dates:Nov. 25, 2017

Frames:
ZWO B 1.25": 25x180" (gain: 76.00) -20C bin 1x1
ZWO G 1.25": 32x180" (gain: 76.00) -20C bin 1x1
ZWO L 1.25": 107x180" (gain: 76.00) -20C bin 1x1
ZWO R 1.25": 30x180" (gain: 76.00) -20C bin 1x1

Integration: 9.7 hours

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 6.28 days

Avg. Moon phase: 38.39%

Bortle Dark-Sky Scale: 3.00

Astrometry.net job: 2052995

RA center: 76.219 degrees

DEC center: -7.219 degrees

Pixel scale: 2.024 arcsec/pixel

Orientation: 272.210 degrees

Field radius: 1.565 degrees

Locations: Atoka dark site, Atoka, Oklahoma, United States

Data source: Unknown

Description

Equipment:
OTA: William Optics GT81 w/0.8x reducer (382mm fl at f/4.7)
Mount: Orion Sirius EQ-G (HEQ-5)
Guidescope: Orion 50mm guidescope
Guiding camera: Orion StarShoot Autoguider
Imaging camera: ZWO ASI1600MM-Cool

Software:
SGP
PHD2
CdC
PixInsight

Acquisition:
Location: Atoka, Oklahoma (Bortle 3)
Dates: 11/18/17, 11/21/17, 11/25/17
Gain: 76 Offset: 15
Camera temp: -20C
L: 107x180"
R: 30x180"
G: 32x180"
B: 25x180"
Total integration time: 9hr 42min
64x darks per calibration
30x flats per calibration
200x bias (master bias in library)

Preprocessing:
Batch PreProcessing script to generate calibrated images
StarAlignment to register all frames to a reference L
LocalNormalization per channel
ImageIntegration
DrizzleIntegration
DynamicCrop each master
DBE on each master

RGB processing:
LinearFit to Blue channel
ChannelCombination to combine
PhotometricColorCalibration
SCNR green
TGV and MMT noise reduction (via Jon Rista's method)
HistogramTransformation x3
CurvesTransformation w/starmask to saturate stars
CurvesTransformation with only nebula masked to saturate nebulosity
ColorSaturation tool to further saturate nebulosity
Slight HistogramTransformation
SCNR green

L processing:
TGV and MMT noise reduction (via Jon Rista's method)
HistogramTransformation
Duplicated the image to create a starless version, using a starmask and several iterations of MMT and MT. Then pushed the faint nebulosity in the starless version using PixelMath expression: "1-(1-$T)*(1-$T)"
Combined the starless version with the image using PixelMath expression "F=0.4; (1-(1-$T)*(1-s)*F)+($T*~F)" followed by the same function but with a value of F=0.2. (s=starless photo).
LocalHistogramEqualization with inverted starmask

Combined L and RGB with LRGBCombination tool
MorphologicalTransformation for slight star reduction
Resampled to 50% for web posting

Comments

Author

ak_astro
Andrew Klinger
License: None (All rights reserved)
2520
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Witch Head Nebula (IC 2118), 





    
        

            Andrew Klinger