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Hemisphere:  Northern  ·  Contains:  Crescent nebula, IC 4996, NGC 6888, The star 34Cyg
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Crescent Nebula, 


Crescent Nebula
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Crescent Nebula

Technical card

Imaging telescopes or lenses: William Optics Gran Turismo 71 APO

Imaging cameras: ASI 1600MM-Pro

Mounts: 10Micron GM1000HPS

Focal reducers: StellarVue 0.8x Reducer/Flattener

Software: PinInsight 1.8  ·  Sequence Generator Pro

Filters: Chroma OIII 3nm  ·  Chroma Ha 3nm

Dates:Sept. 10, 2018Sept. 11, 2018

Chroma Ha 3nm: 83x300" (gain: 139.00) -20C bin 1x1
Chroma OIII 3nm: 85x300" (gain: 139.00) -20C bin 1x1

Integration: 14.0 hours

Darks: ~8

Flats: ~10

Avg. Moon age: 1.41 days

Avg. Moon phase: 2.56%

Bortle Dark-Sky Scale: 8.00

Mean FWHM: 2.95

Basic astrometry details job: 2278287

RA center: 20h 12' 33"

DEC center: +38° 22' 8"

Pixel scale: 2.307 arcsec/pixel

Orientation: 173.671 degrees

Field radius: 1.570 degrees

Resolution: 3908x2956

Data source: Backyard


Crescent Nebula taken with William Optics 71gt with .8x focal reducer/corrector and ASI 1600mm pro.

There are not very many calibration frames as this was a rundown to make sure that my mount problems that appeared over the summer had been successfully worked out. It looks like they have been.

Processed in Pixinsight:
-Calibration and Registration for HA and OIII
HA and OIII separately:
-Minor deconvolution as the stars started looking weird after only a few iterations
-MMT (5 layers). OIII: Did nothing on layer 2 as that had most of the soap bubble and I did not want to risk having MMT disrupt it.
-Masked stretch to background of 0.125 and clipping % = 0

Combined HA and OIII in Pixel Math: Red = HA, Green = OIII, Blue = OIII

Processing on Combined Image:
-A few iterations of Histogram transformation in RGB until Red histogram was stretched much further than Green/Blue. There is a lot more HA than OIII, so this happened quite quickly.
-A few small iterations of Blue and Green separately to bring blue/green up to nearly Red's level, not quite. Did not want to blow out OIII.
-A few very minor iterations of Curves with an S-curve.



License: Attribution Creative Commons

Sky plot

Sky plot


Crescent Nebula,