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Contains:  Crescent nebula, NGC 6888
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NGC 6888 - Crescent Nebula, 





    
        

            Linda
NGC 6888 - Crescent Nebula

Technical card

Resolution: 2592x2232

Dates:July 30, 2019Aug. 10, 2019Aug. 12, 2019Aug. 29, 2019Sept. 7, 2019

Frames:
Astrodon Gen 2 Series I Blue: 239x60" (gain: 76.00) -15C bin 1x1
Astrodon Gen 2 Series I Green: 236x60" (gain: 76.00) -15C bin 1x1
Astrodon Gen 2 Series I Red: 275x75" (gain: 76.00) -15C bin 1x1

Integration: 13.6 hours

Darks: ~50

Flats: ~25

Flat darks: ~50

Avg. Moon age: 17.39 days

Avg. Moon phase: 47.64%

Astrometry.net job: 2962400

RA center: 20h 11' 35"

DEC center: +38° 32' 20"

Pixel scale: 1.620 arcsec/pixel

Orientation: 69.875 degrees

Field radius: 0.770

Locations: Camp Highroad, Middleburg, VA, United States; Home, Broadlands, VA, United States

Data source: Backyard

Description

This is a combination of five nights of data split between SGP and NINA. Four nights were at home and one was at a club site that is slightly darker.

This was difficult to process. There were so many tiny stars that they overwhelmed the image. It made the image look like it was printed on a fuzzy sweater and nothing I did really helped all that much.

The text below is for the initial revision. Revisions B-D are a fresh reprocessing. I'd love to hear which version people prefer and why.

I ended up trying a bunch of different techniques to tame them but though they worked (Adam Block's worked the best) the tiny stars were unaffected. In desperation I created a a range mask that tried to select just the background and those barely visible tiny stars. I applied that to the image and the convolved those stars into oblivion. Who knew I had such power? :)

I then applied Adam's star de-emphasis routine on the remaining stars and I decided I could live with the result.

The background became artificially smooth but the offending stars were gone. I'm fairly sure I did some damage to the faintest detail in the image but compared to a background that was nearly solid stars it seemed a reasonable trade off. I really need narrowband filters...

For now this will have to do. If anyone has any ideas or would like to try the data, please let me know!

Revision F is a new processing that was the same as the others through PCC but then:
TGV Denoise
Masked Stretch
Star Reduction Script
Adv Sharpening Script
Curves for contrast

Most people I've shown this to locally seem to prefer revision F but I'd love to hear your opinions as to which you prefer and why.

Comments

Author

ac4lt
Linda
License: Attribution-NonCommercial-ShareAlike Creative Commons
2212
Like

Revisions

  • NGC 6888 - Crescent Nebula, 





    
        

            Linda
    Original
  • NGC 6888 - Crescent Nebula, 





    
        

            Linda
    C
  • NGC 6888 - Crescent Nebula, 





    
        

            Linda
    D
  • NGC 6888 - Crescent Nebula, 





    
        

            Linda
    E
  • Final
    NGC 6888 - Crescent Nebula, 





    
        

            Linda
    F

C

This is a reprocessing from scratch that tries to hold on to more detail although it retains more stars.

D

This takes Rev C and takes that orangish cast and shifts it to red. I don't know which is more accurate from a photometry perspective (though the orange came in via PCC) but I preferred this aesthetic.

E

This takes Rev D and pushes the background down some more for non-red's increasing contrast with the nebula and bring down the stars a bit more.

F

This is a reprocessing from scratch using the techniques I used on the eastern veil. This doesn't try to bring out every last bit of nebulosity but instead focuses on clarity and perceived sharpness. Which version do you prefer?

Sky plot

Sky plot

Histogram

NGC 6888 - Crescent Nebula, 





    
        

            Linda