Hemisphere:  Southern  ·  Constellation: Orion (Ori)  ·  Contains:  Flame Nebula  ·  IC 434  ·  IC 435  ·  NGC 2023  ·  NGC 2024  ·  Orion B  ·  The star Alnitak (ζOri)  ·  The star σOri
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Horsehead Nebula (IC 434) - Narrowband + Blue, 



    
        

            rhedden
Horsehead Nebula (IC 434) - Narrowband + Blue
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Horsehead Nebula (IC 434) - Narrowband + Blue

Technical card

Imaging telescopes or lenses: Sky-Watcher Espirit 100ED Super Apo

Imaging cameras: QSI 660 WS

Mounts: Software Bisque Paramount MX

Guiding telescopes or lenses: Stellarvue SV F60M3

Focal reducers: Starizona APEX ED .65

Software: Topaz Labs Topaz DeNoise AI  ·  SiriL 0.99.6  ·  GIMP  ·  Deep Sky Stacker  ·  Fitswork 4  ·  Regim  ·  Software Bisque The SkyX Professional  ·  Imagenomic LLC Noiseware

Filters: Orion Extra Narrowband Filter OIII 1.25"  ·  Orion Extra Narrowband Filter Ha 1.25"  ·  Astrodon 31mm LRGB E Series Gen 2 1.25"

Accessory: orion starshoot autoguider


Dates:Dec. 6, 2020Jan. 7, 2021Feb. 4, 2021

Frames:
Astrodon 31mm LRGB E Series Gen 2 1.25": 19x120" -18C bin 1x1
Orion Extra Narrowband Filter Ha 1.25": 24x240" -20C bin 1x1
Orion Extra Narrowband Filter Ha 1.25": 27x240" -22C bin 1x1
Orion Extra Narrowband Filter OIII 1.25": 20x240" -18C bin 1x1

Integration: 5.4 hours

Avg. Moon age: 21.93 days

Avg. Moon phase: 52.28%

Bortle Dark-Sky Scale: 4.00


Basic astrometry details

Astrometry.net job: 4213226

RA center: 5h 40' 5"

DEC center: -2° 30' 36"

Pixel scale: 1.312 arcsec/pixel

Orientation: 106.105 degrees

Field radius: 1.248 degrees


Resolution: 4363x5284

Locations: Back Yard - New York, Pittstown, NY, United States

Data source: Backyard

Description

This image is a composite of two synthetic RGB combinations of H-alpha, Oiii, and Blue filters.

Combination HOO: Red = H-alpha, Green = (80% Oiii, 20% H-alpha), Blue = Oiii
Combination HOB: Red = H-alpha, Green = (80% Oiii, 20% H-alpha), Blue = Blue

Combination "HOO" was used for the nebula colors and blue stars; combination "HOB" was used for star colors on orange, yellow, and off-white stars.

The luminance layer is mostly H-alpha, except the Blue data were added using "lighten mode" to enhance the reflection nebulae. The problematic halos around bright blue stars (e.g. Alnitak) were reduced by using entirely H-alpha close to the stars.

This image required a lot of processing work to remove halos and ghosts from bright stars. While the damage is minimal in the final image, I don't want anyone to think that the filters and optics used produced magical data without any halo around Alnitak. :)

Also, it is worth noting that the "HOO" data were further manipulated in GIMP by changing the composition of the green channel using the Channel Mixer feature. While the resulting nebula has pleasing (false) colors, all of the stars turned blue. Importing the pseudo-RGB star colors from the HOB combination was very tedious, and it required manually creating a star mask, which took up several hours. I will think twice before attempting another project with this filter combination.

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