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Contains:  NGC 6334
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NGC6334 - The Cat's Paw Nebula, 


            Andrew Klinger
NGC6334 - The Cat's Paw Nebula

NGC6334 - The Cat's Paw Nebula

Technical card

Resolution: 4481x3289

Dates:May 29, 2017

ZWO B 1.25": 8x180" -20C bin 1x1
ZWO G 1.25": 8x180" -20C bin 1x1
ZWO L 1.25": 38x180" -20C bin 1x1
ZWO R 1.25": 8x180" -20C bin 1x1

Integration: 3.1 hours

Darks: ~60

Flats: ~30

Bias: ~200

Avg. Moon age: 4.23 days

Avg. Moon phase: 18.89%

Bortle Dark-Sky Scale: 3.00 job: 2052952

RA center: 259.795 degrees

DEC center: -35.429 degrees

Pixel scale: 2.020 arcsec/pixel

Orientation: 89.399 degrees

Field radius: 1.560 degrees

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


The Cat's Paw Nebula is an emission and star forming region in the constellation Scorpius. It was a very low target for me as I am shooting from 34°N, the target never rose above 21°. The RGB frames were also shot through a thin layer of clouds. This is my first light with the new camera, I'm super pleased with the results given the low integration time and position of the target!

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: 5/24/17, 5/29/17
Gain: 0 Offset: 10
Camera temp: -20C
L: 38x180"
R: 8x180"
G: 8x180"
B: 8x180"
Total integration time: 3hr 6min
60x darks
30x flats per filter
200x bias (master bias in library)

Batch PreProcessing script to generate calibrated/registered images
ImageIntegration (Linear Fit rejection for L, Percentile rejection for RGB)
Dynamic Crop the masters
DBEx2 on each master

RGB processing:
LinearFit to Red channel
ChannelCombination to combine
SCNR green
TGV and MMT noise reduction (via Jon Rista's method)
SCNR green
HistogramTransformation x3
CurvesTransformation w/starmask to saturate stars
CurvesTransformation w/~starmask to saturate nebulosity
CurvesTransformation w/Lmask(minus stars) to further saturate nebula
CurvesTransformation for contrast
SCNR green

L processing:
MMT (slight NR)
HistogramTransformation x3 using a starmask to manually perform a masked stretch
CurvesTransformation small stretch
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).
HistogramTransformation to move black point
LocalHistogramEqualization with inverted starmask
CurvesTransformation for contrast
MorphologicalTransformation for star reduction

Combined L and RGB with the script "LRVB-AIP"
SCNR red with starmask to dim annoyingly bright red stars
SCNR green
CurvesTransformation for slight contrast
HistogramTransformation to bring the green channel in just a tad because the image was too red.



Andrew Klinger
License: None (All rights reserved)

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NGC6334 - The Cat's Paw Nebula, 


            Andrew Klinger