Hemisphere:  Northern  ·  Constellation: Cygnus (Cyg)  ·  Contains:  Crescent nebula  ·  NGC 6888  ·  The star 34Cyg
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Crescent Nebula (NGC6888) imaged in SHO, 



    
        

            Andrew Klinger
Crescent Nebula (NGC6888) imaged in SHO
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Crescent Nebula (NGC6888) imaged in SHO

Getting plate-solving status, please wait...
Crescent Nebula (NGC6888) imaged in SHO, 



    
        

            Andrew Klinger
Crescent Nebula (NGC6888) imaged in SHO
Powered byPixInsight

Crescent Nebula (NGC6888) imaged in 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:July 17, 2017Sept. 1, 2019

Frames:
Astrodon OIII 3nm: 58x300" (4h 50') (gain: 200.00) -10C bin 1x1
Astrodon SII 3nm: 56x300" (4h 40') (gain: 200.00) -10C bin 1x1
Ha 5nm: 154x180" (7h 42') (gain: 200.00) -10C bin 1x1

Integration: 17h 12'

Darks: 64

Flats: 30

Bias: 200

Avg. Moon age: 12.65 days

Avg. Moon phase: 24.35%

Bortle Dark-Sky Scale: 4.33


Basic astrometry details

Astrometry.net job: 2909257

RA center: 20h14m51s

DEC center: +38°4210

Pixel scale: 2.878 arcsec/pixel

Orientation: 178.748 degrees

Field radius: 1.565 degrees


Resolution: 3153x2324

Locations: Atoka dark site, Atoka, Oklahoma, United States; Backyard, Flower Mound, Texas, United States

Data source: Backyard

Description

Here shown is a widefield view of the Crescent Nebula and surrounding nebulosity in the constellation Cygnus. In this false-color image Hydrogen(Ha) and Sulfur(SII) are shown as the warmer colors and Oxygen(OIII) is shown as blue. There are a few notable OIII structures that are not present in the other channels. Front and foremost is the shell around the Crescent nebula itself, and if you look to the top-center of the image you will see a perfectly shaped blue circle known as the Soap Bubble Nebula.

I recently captured the OIII and SII data to combine with my 2017 Ha data on this target.

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:

DeepSkyDad Autofocuser AF1

QHYCCD PoleMaster

Software:

SGP

PHD2

CdC

PixInsight

Acquisition:

Location: Flower Mound, TX (Bortle 7), Atoka, OK (Bortle 3)

Dates: 7/12/17, 7/18/17, 6/28/19, 9/1/19

Gain: 200 Offset: 50

Camera temp: -10C

Ha: 154x180" Astrodon 5nm

SII: 56x300" Astrodon 3nm

OIII: 58x300" Astrodon 3nm

Total integration time: 17hr 12min

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

DrizzleIntegration

DynamicCrop

DBE

Luminance Processing:

Duplicated the master Ha and Oiii to use as the luminance

Deconvolution on each Ha and Oiii

Created a synthetic luminance using PixelMath equation: "(Ha)+(max(Ha,(1.5*Oiii)))"

ArcsinhStretch and HistogramTransformation to bring to non-linear

ExponentialTransformation to push nebulosity

LocalHistogramEqualization

MultiscaleLinearTransform for sharpening

MorphologicalTransformation to reduce star size

UnsharpMask to harden up soft stars caused by previous step

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++

DBE on the SII and OIII channel to help corners

LinearFit to Ha

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

R: Sii

G: Ha

B: Oiii

Created an HOO image as well with this PixelMath formula (to blend later):

R: iif(ha>.15,ha,(ha*.+(oiii*.2))

G: iif(ha>0.5,1-(1-oiii)*(1-(ha-0.5)),oiii*(ha+0.5))

B: iif(oiii>.1,oiii,(ha*.3)+(oiii*.2))

SHO Tonemap Processing:

Invert > SCNR Green > Invert to remove magenta

CurvesTransformation to balance colors

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

HOO Tonemap Processing:

Invert > SCNR Green > Invert to remove magenta

HistogramTransformation to balance colors

CurvesTransformation to further balance colors

Combined SHO and HOO tonemap with PixelMath equation: "min(SHO,HOO)"

CurvesTransformation to brighten the image up a bit

SCNR Green

Combined Tonemap with Luminance using LRGBCombination:

Resampled to 35% for web posting

Comments

Sky plot

Sky plot

Histogram

Crescent Nebula (NGC6888) imaged in SHO, 



    
        

            Andrew Klinger

In these public groups

Narrowband imaging