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Contains:  Bubble nebula, NGC 7510, NGC 7538, NGC 7635
Getting plate-solving status, please wait...

The Bubble and Lobster Claw Nebula (NGC7635 & Sh2-157) 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:Aug. 19, 2019Sept. 3, 2019

Ha 5nm: 155x300" (gain: 200.00) -10C bin 1x1
Astrodon OIII 3nm: 89x600" (gain: 200.00) -10C bin 1x1
Astrodon SII 3nm: 93x600" (gain: 200.00) -10C bin 1x1

Integration: 43.2 hours

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 11.49 days

Avg. Moon phase: 54.41%

Bortle Dark-Sky Scale: 7.00

Basic astrometry details job: 2944209

RA center: 23h 17' 21"

DEC center: +60° 39' 46"

Pixel scale: 4.042 arcsec/pixel

Orientation: 93.409 degrees

Field radius: 1.570 degrees

Resolution: 2229x1688

Locations: Backyard, Flower Mound, Texas, United States

Data source: Backyard


This chunk of sky in the constellation Cassiopeia is quite busy with nebula. You can find the impressive structure of the Bubble Nebula in the lower left, and the Lobster Claw in the upper right of the image. The semi-circle of red hydrogen dust on the left edge is the nebula Sh2-161, with the small but bright nebula NGC7538 sitting on the upper left.

This false-color image shows the Hydrogen and Sulfur as the warmer tones and Oxygen as blue.

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

DeepSkyDad Autofocuser AF1
QHYCCD PoleMaster


Location: Flower Mound, TX (Bortle 7)
Dates: 8/19/19, 8/20/19, 9/3/19, 9/4/19, 9/5/19, 9/6/19, 9/7/19
Gain: 200 Offset: 50
Camera temp: -10C
Ha: 155x300" Astrodon 5nm
SII: 93x600" Astrodon 3nm
OIII: 89x600" Astrodon 3nm
Total integration time: 43hr 15min
64x darks per calibration (master from library)
30x flats per calibration
200x bias per calibration (master from library)

Batch PreProcessing script to generate calibrated images

Luminance Processing:
Duplicated the master Ha to use as the luminance
ArcsinhStretch and HistogramTransformation to bring to non-linear
Created a duplicate starless version using StarNet++
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 F=0.2, (s=starless photo).
MultiscaleLinearTransform for sharpening
MorphologicalTransformation for star size reduction
UnsharpMask to harden up reduced stars

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++
LinearFit to Ha

Combined prepared Sii, Ha, and Oiii masters with ChannelCombination:
R: Sii
G: Ha
B: Oiii

Tonemap Processing:
Invert > SCNR Green > Invert to remove magenta
Several a/b channel CurvesTransformations using ColorMasks to alter the colors to an aesthetically pleasing palette
HDRMultiscaleTransform on the Bubble
SCNR green on the background
CurvesTransformation to balance colors

Combined Tonemap with Luminance using LRGBCombination:
HistogramTransformation to balance colors
CurvesTransformation for slight contrast
Resampled to 25% for web posting



Andrew Klinger

Sky plot

Sky plot


The Bubble and Lobster Claw Nebula (NGC7635 & Sh2-157) imaged in SHO, 


            Andrew Klinger

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Narrowband imaging