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Contains:  Crescent nebula, NGC 6888, The star 34Cyg
Getting plate-solving status, please wait...
Crescent Nebula in Ha (NGC6888), 


            Andrew Klinger
Crescent Nebula in Ha (NGC6888)

Crescent Nebula in Ha (NGC6888)

Technical card

Imaging telescope or lens:William Optics GT-81

Imaging camera:ZWO ASI1600MM-Cool

Mount:Orion Sirius EQ-G (HEQ5)

Guiding telescope or lens:Orion 50 mm Guide Scope

Guiding camera:Orion Star Shoot Auto Guider

Focal reducer:William Optics Flat 6A

Software:Cartes du CielPHD2EQMODPixInsightSequence Generator Pro

Filter:Astrodon Ha 5nm


Resolution: 3378x4498

Dates:July 12, 2017

Frames:Astrodon Ha 5nm: 154x180" (gain: 200.00) -15C bin 1x1

Integration: 7.7 hours

Darks: ~64

Flats: ~30

Bias: ~200

Avg. Moon age: 17.86 days

Avg. Moon phase: 89.56%

Bortle Dark-Sky Scale: 7.00 job: 2052967

RA center: 303.727 degrees

DEC center: 38.704 degrees

Pixel scale: 2.017 arcsec/pixel

Orientation: 89.109 degrees

Field radius: 1.576 degrees

Locations: Backyard, Flower Mound, Texas, United States

Data source: Unknown


This image shows the Crescent Nebula diving towards the larger structure that is part of the Gamma Cygni Nebula. This is my first time using a narrowband filter, specifically the Astrodon 5nm Hydrogen-alpha filter. Super pleased with the results given I was imaging from a red/white zone. RGB data will be coming later this month for a complete image!

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: Arlington, TX (Bortle 7)
Dates: 7/12/17, 7/18/17
Gain: 200 Offset: 50
Camera temp: -14C
Ha: 154x180" Astrodon 5nm
Total integration time: 3hr 12min
64x darks
30x flats
200x bias

Batch PreProcessing script to generate calibrated/registered images
ImageIntegration (Linear Fit rejection)

TGV noise reduction (via Jon Rista's method)
HistogramTransformation x2
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
DarkStructureEnhance Script



Andrew Klinger
License: None (All rights reserved)

Sky plot

Sky plot


Crescent Nebula in Ha (NGC6888), 


            Andrew Klinger