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Contains:  Crescent nebula, NGC 6888
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Crescent Nebula in Synthetic RGB, 





    
        

            Frank Kane
Crescent Nebula in Synthetic RGB

Crescent Nebula in Synthetic RGB

Technical card

Resolution: 10800x7200

Dates:May 25, 2019

Frames: 48x240"

Integration: 3.2 hours

Avg. Moon age: 21.09 days

Avg. Moon phase: 61.16%

Astrometry.net job: 2727340

RA center: 20h 12' 26"

DEC center: +38° 13' 37"

Pixel scale: 0.244 arcsec/pixel

Orientation: 85.421 degrees

Field radius: 0.439

Locations: My Driveway, Winter Springs, FL, United States

Data source: Backyard

Description

The Crescent Nebula (NGC 6888) imaged with narrowband filters from a suburban driveway, converted to RGB using an algorithm that tries to recreate its natural appearance from narrowband data. It's a way to beat light pollution while still getting fairly natural-looking colors. The details are at http://boldly-going.com/2019/05/21/beating-light-pollution-with-a-new-synthetic-rgb-algorithm/ and you'll also find the larger image this was cropped from there.

For this image I derived a slightly different RGB mapping that takes into account the fact that my filters are narrow enough to exclude the second O3 emission line, and synthesizes it as well:

R = 0.5*Ha + 0.5*SII
G = 0.695*OIII + 0.094*Ha
B = 0.411*OIII + 0.1*Ha

It didn't make much of a visual difference, but in theory it's a little bit closer to reality.

Other processing notes:
- I love Mure Denoise
- OIII and SII data wasn't awesome, so I used Hydrogen-alpha as a luminance channel. Unfortunately this means a faint shell of OIII ahead of the nebula got lost, but the image is significantly sharper as a result.
- I de-saturated everything a little outside of the Crescent itself, to make the stars a little less distracting in the image.

Comments

Author

fkane
Frank Kane
License: None (All rights reserved)
380
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Revisions

  • Crescent Nebula in Synthetic RGB, 





    
        

            Frank Kane
    Original
  • Final
    Crescent Nebula in Synthetic RGB, 





    
        

            Frank Kane
    B

B

Cleaned up the background to make it print-quality.

Sky plot

Sky plot

Histogram

Crescent Nebula in Synthetic RGB, 





    
        

            Frank Kane