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sh2-136 "Ghost Nebula" in Cepheus - LRGB, 





    
        

            Daniel.P
sh2-136 "Ghost Nebula" in Cepheus - LRGB

sh2-136 "Ghost Nebula" in Cepheus - LRGB

Acquisition type: Electronically-Assisted Astronomy (EAA)

Technical card

Resolution: 4569x3430

Dates:Aug. 2, 2019Aug. 3, 2019Aug. 4, 2019Aug. 5, 2019

Frames:
ZWO new B: 30x120" (gain: 139.00) -15C bin 1x1
ZWO new B: 17x300" (gain: 50.00) -15C bin 1x1
ZWO new G: 30x120" (gain: 139.00) -15C bin 1x1
ZWO new G: 29x300" (gain: 50.00) -15C bin 1x1
ZWO new L: 60x120" (gain: 139.00) -15C bin 1x1
ZWO new L: 68x300" (gain: 50.00) -15C bin 1x1
ZWO new R: 30x120" (gain: 139.00) -15C bin 1x1
ZWO new R: 30x300" (gain: 50.00) -15C bin 1x1

Integration: 17.0 hours

Avg. Moon age: 3.31 days

Avg. Moon phase: 13.30%

Mean SQM: 21.30

Mean FWHM: 2.60

Astrometry.net job: 2986627

RA center: 319.102 degrees

DEC center: 68.259 degrees

Pixel scale: 0.908 arcsec/pixel

Orientation: 180.066 degrees

Field radius: 0.721 degrees

Locations: Duc, Prayssas, Lot et Garonne, France

Data source: Backyard

Description

I spent most of these 4 moonless nights with dark sky (around 21.3 SQM) to image this nebula with LRGB filters.

17 hours is currently my longest total exposure on a single target. Stars with mag 22.5 should be visible (with SNR=5) on the image.

My AO was off, and I use multistar guiding with PHD2 directly on the CEM120EC2 mount. It worked well but apparently, I was better not using to fast corrections (it seems to interfere with the encoders work). I used typically 2 sec guide steps. My objective is to use back AO with faster guide steps.

The image is color balanced on stars.

The processing was done in PI as follow :
For each L, R, G, B channels :
- Images Calibration (Dark Substraction, deFlat)
- Cosmetic Correction
- Image Registration
- Image Integration
- Mure Denoise
Then :
- Create super L image (integration of L and RGB individual channel)
- Create RGB image and color balance using R,G,B channels
- LRGB combination with superL
- DBE
- Color balance on stars
- Color Saturation masked (and desaturate bkg)
- Deconvolution masked with 1.8 pixel psf
- Background extraction
- Going NL using HT
- TGV denoise (no mask)
- Local Histogram Equalisation (at 90 pix scale)
- Color Saturation masked using stars to boost stars color
- Color Balance on stars
- Color Saturation masked using stars to boost stars color
- Deflip
- Crop

Final image adjustments performed in Iphoto on Imac :
- levels adjustments

Comments

Author

Daniel.P
Daniel.P
License: None (All rights reserved)
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Revisions

  • sh2-136 "Ghost Nebula" in Cepheus - LRGB, 





    
        

            Daniel.P
    Original
  • Final
    sh2-136 "Ghost Nebula" in Cepheus - LRGB, 





    
        

            Daniel.P
    C

C

with star color deringing

Sky plot

Sky plot

Histogram

sh2-136 "Ghost Nebula" in Cepheus - LRGB, 





    
        

            Daniel.P