Cookie consent

AstroBin saves small pieces of text information (cookies) on your device in order to deliver better content and for statistical purposes. You can disable the usage of cookies by changing the settings of your browser. By browsing AstroBin without changing the browser settings, you grant us permission to store that information on your device.

I agree
Contains:  Witch Head nebula, IC 2118, NGC 1752, The star ψEri
Getting plate-solving status, please wait...
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

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 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


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


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)

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

RGB processing:
LinearFit to Blue channel
ChannelCombination to combine
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)
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



Andrew Klinger
License: None (All rights reserved)

Sky plot

Sky plot


Witch Head Nebula (IC 2118), 


            Andrew Klinger