M42 - The Orion Nebula (Steve Ludwig)

M42 - The Orion Nebula

Equipment

- Main scope: Bresser Messier 10" Newton (254/1270)

- Main camera: Nikon D3300 (unmodified)

- Guide scope: Orion AC 50/162 Deluxe Mini

- Guide camera: ZWO ASI 290MC

- Mount: Skywatcher EQ6-R

- Explore Scientific HR coma corrector

Acquisition

- 113 lights x 150 s = 4 h 42 min

- no dark, flat, bias frames

- no filters

- ISO 200

- Bortle 4

Processing

- stacked in DSS

-> bilinear debayer method & median kappa sigma clipping

- unmodified TIF opened in PixInsight

-> STF stretch

-> rotation

-> crop

-> dynamic background extraction

-> background neutralization

-> color calibration

-> histogram transformation

-> multiscale linear transform to sharpen the whole image

-> use of starnet++ module to separate background and stars

-> multiscale linear transform to further sharpen background only

-> pixel math to recombine background and stars

-> resample 50%

-> ACDNR with lightness mask to reduce noise of darker areas

-> final curves transformation to increase overall brightness a bit

-> saved as jpg

New in Revision B

-> masked stretch to increase contrast of dark regions

-> masked ACDNR to reduce noise in the areas that have been brought out by masked stretch

-> curves transformation to increase overall saturation

-> histogram transformation to lower black point by 5%

-> background neutralization o remove bluish tint from the image

-> saved as jpg

New in Revision C

-> histogram transformation: black point increase of red channel to get more neutral background

-> histogram transformation: overall black point increase to undo half of the black point reduction from revision B

New in Revision D

-> TGV Denoise with maximum edge protection and low strength to decrease noise without losing details or dim stars

Original
C
D
E
Final
F

C

Description: Some further histogram fine-tuning: I increased the black point of the red channel a bit to get a slightly more neutral background. Furthermore, I increased the overall black point a bit (+0.025) after filling in some zeros at the low end in the revision before.

Uploaded: ...

D

Description: For revision D, I applied another run of "TGV Denoise" with low strength and maximum edge protection. This helped to further reduce noise without losing fine details and dim stars. Furthermore, I slightly cropped the image to get rid of the distractive Iota Orionis star halo.

Uploaded: ...

E

Description: In revision E, I used another run of ACDNR to reduce noise in the outer, dark regions of the image. Now there is a smooth transition between bright and dark parts. I'm really happy with how it turned out in the end. ;)

Uploaded: ...

F

Description: After hesitating to apply any HDR processes to my M42 image, I finally tried it. Actually, I really like M42 with a natural, bright core. However, in the latest revision I tried to bring out more detail in the core without losing too much of its brightness. To achieve that, I applied the following process steps:

- HDR Multiscale Transform to bring out detail in the core
- SCNR green to remove greenish tint (especially around the core)
- Pixel Math to blend the earlier version with the HDR version (70%/30%) which gave a good balance of detail and brightness
- Curves Transformation to increase saturation a bit

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	4271795
PixInsight job	1WR3VZXYY2QLADLB5E8MRKCD60Z6BYKC
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	05h34m58s.20
RA (top/left)	05h37m10s.67
RA (top/right)	05h34m06s.35
RA (bottom/right)	05h32m45s.29
RA (bottom/left)	05h35m49s.77

Dec (center)	-05°24′54″.8
Dec (top/left)	-05°26′36″.8
Dec (top/right)	-04°54′27″.4
Dec (bottom/right)	-05°23′10″.10
Dec (bottom/left)	-05°55′23″.3

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