Hemisphere:  Southern  ·  Constellation: Scorpius (Sco)  ·  Contains:  NGC 6357
NGC6357 - The Scorpion in Scorpius (SHO), 



    
        

            Andrew Klinger
NGC6357 - The Scorpion in Scorpius (SHO)
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NGC6357 - The Scorpion in Scorpius (SHO)

NGC6357 - The Scorpion in Scorpius (SHO), 



    
        

            Andrew Klinger
NGC6357 - The Scorpion in Scorpius (SHO)
Powered byPixInsight

NGC6357 - The Scorpion in Scorpius (SHO)

Technical card

Imaging telescopes or lenses: William Optics GT-81

Imaging cameras: ZWO ASI1600MM-Cool

Mounts: Orion Sirius EQ-G (HEQ5)

Guiding telescopes or lenses: Orion 50 mm Guide Scope

Guiding cameras: Orion Star Shoot Auto Guider

Focal reducers: William Optics Flat 6A

Software: Sequence Generator Pro  ·  PHD2  ·  Cartes du Ciel  ·  EQMOD  ·  PixInsight

Filters: Astrodon OIII 3nm  ·  Astrodon SII 3nm  ·  Ha 5nm

Accessory: PoleMaster


Dates:May 31, 2019

Frames:
Astrodon OIII 3nm: 33x300" (2h 45') (gain: 200.00) -10C bin 1x1
Astrodon SII 3nm: 34x300" (2h 50') (gain: 200.00) -10C bin 1x1
Ha 5nm: 35x300" (2h 55') (gain: 200.00) -10C bin 1x1

Integration: 8h 30'

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 26.57 days

Avg. Moon phase: 9.60%

Bortle Dark-Sky Scale: 3.00


Basic astrometry details

Astrometry.net job: 2783068

RA center: 17h 26' 33"

DEC center: -34° 11' 38"

Pixel scale: 2.022 arcsec/pixel

Orientation: 1.278 degrees

Field radius: 1.560 degrees


Resolution: 4482x3282

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

Data source: Traveller

Description

There are a lot of names for this intricate nebula, however none of them really seem to fit the bill. "The Lobster Nebula" as well as the "War and Peace Nebula" are used often but I personally see a scorpion with raised claws and a faint curved tail. Not to mention this nebula resides in the constellation Scorpius, a fitting home. So hear me out astronomical community and lets make this happen!

In this false-color narrowband image, I display the Sulphur and Hydrogen emissions as the warm red-orange colors and the Oxygen emissions as the teal-blue range. I typically save narrowband imaging for home, but since this target never rose above 22° I used my dark site's unobstructed view to capture this nebula. In the core of this nebula lie some of the most massive stars known, and the surrounding nebulosity shows off a chaotic display of gas and dark dust.

Equipment:

OTA: William Optics GT81 w/0.8x reducer (382mm fl at f/4.7)

74mm aperture stop-down ring (brings scope to f/5.2)

Mount: Orion Sirius EQ-G (HEQ-5)

Guidescope: Orion 50mm guidescope

Guiding camera: Orion StarShoot Autoguider

Imaging camera: ZWO ASI1600MM-Cool

Accessories:

QHYCCD PoleMaster

Software:

SGP

PHD2

CdC

PixInsight

Starnet++

Acquisition:

Location: Atoka, OK (Bortle 3)

Dates: 5/31/19, 6/26/19, 6/27/19

Gain: 200 Offset: 50

Camera temp: -10C

Sii: 34x300" Astrodon 3nm

Ha: 35x300" Astrodon 5nm

Oiii: 33x300" Astrodon 3nm

Total integration time: 8hr 30min

64x darks per calibration (master from library)

30x flats per calibration

200x bias per calibration (master from library)

Preprocessing:

Batch PreProcessing script to generate calibrated images

StarAlignment

LocalNormalization

ImageIntegration

DynamicCrop each master

DBE each master

Luminance Processing:

Duplicated the master Ha to use as the luminance

Deconvolution

TGV noise reduction (via Jon Rista's method)

ArcsinhStretch and HistogramTransformation to bring to non-linear

HDRMultiscaleTransform to reveal core

LocalHistogramEqualization

MultiscaleLinearTransform for sharpening

CurvesTransformation for slight contrast

Preparing separate Sii, Ha, and Oiii linear masters for tonemapping (applied to each master individually):

TGV & MMT noise reduction (via Jon Rista's method)

ArcsinhStretch and HistogramTransformation to bring to non-linear

Removed stars via StarNet++

Further removed background artifacts with MMT

Combined prepared Sii, Ha, and Oiii masters with ChannelCombination:

R: Sii

G: Ha

B: Oiii

Tonemap Processing:

Invert>SCNR Green>Invert to remove magenta

DBE to help with uneven color casts

Several a/b channel CurvesTransformations using ColorMasks to alter the colors to an aesthetically pleasing palette

CurvesTransformation for saturation

CurvesTransformation for slight contrast

Combined Tonemap with Luminance using LRGBCombination

CurvesTransformation to balance background color

MorphologicalTransformation for slight star reduction

UnsharpMask with a StarMask to harden up the soft stars a tad

Comments

Sky plot

Sky plot

Histogram

NGC6357 - The Scorpion in Scorpius (SHO), 



    
        

            Andrew Klinger

In these public groups

Narrowband imaging