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


NGC 6888 - Crescent Nebula

NGC 6888 - Crescent Nebula

Technical card

Resolution: 4656x3520

Dates:May 10, 2018

AstroDon 5nm Ha filter: 3x300" (gain: 139.00) -15C bin 1x1
AstroDon 5nm OIII filter: 3x300" (gain: 139.00) -15C bin 1x1

Integration: 0.5 hours

Darks: ~7

Flats: ~11

Flat darks: ~5

Avg. Moon age: 24.37 days

Avg. Moon phase: 27.23%

Mean SQM: 21.00

Mean FWHM: 3.40

Temperature: 10.00 job: 2253981

RA center: 20h 12' 40"

DEC center: +38° 19' 48"

Pixel scale: 0.914 arcsec/pixel

Orientation: 179.646 degrees

Field radius: 0.741

Locations: Duc, Prayssas, Lot et Garonne, France

Data source: Backyard


Last may, I selected NGC6888 to test my new OIII 5nm filter together with the Ha.

The APO still need some further collimation.
But more importantly, I struggle to get my AZ mount to work properly. It showed large and erratic periodic error (not sure so periodic after all). Even the the AO was not able to correct as it exceeded AO limits. This is why the resulting image is not sharp and show some "trails".

But I found the filter very good at displaying faint OIII extensions of the nebula, despite the short integration time (2 x 15 mn). These extensions where not visible on previous image taken with QHY8L on my C8 even after few hours of integration.

The processing was done in PI as follow :
For each Ha & OIII channels :
- Flat Field Dark Substraction
- Flat Field Integration
- Images Calibration (Dark Substraction and FF correction)
- Cosmetic Correction
- Image Registration
- Image Integration
- Noise Reduction (Demure)
Create HOO color image :
- Nonlinear Image Creation
- Color Balance on the nebula
- SCNR noise reduction (green neutral)
Final image adjustments performed in Iphoto on Imac (levels adjustments)

Improvements planned :
Finalise APO collimation
Increase sub expose duration to 10 to 20 mn to benefit from the dark sky
Acquire RGB data to display stars in more natural colors
Get my mount work again or change mount (this is what I did finally)



License: None (All rights reserved)

Sky plot

Sky plot


NGC 6888 - Crescent Nebula, 



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