M8 - Lagoon Nebula 2 panel Mosaic (Kevin Morefield)

M8 - Lagoon Nebula 2 panel Mosaic

2019 commentary: Having shot this before I knew I wanted to do a mosaic of the Lagoon to capture more of the nebulosity that surrounds the bright center. I also wanted to present the detail in the core that the SII band reveals. My FOV is square so this image is two FOVs side by side.

M8 only spends a couple of hours above 20 degrees for me. And I shot 67 hours of subs so this took a while! Only 31 hours of the subs were used. Being so low in the sky the atmospheric refraction warped the field quite a bit. I was not able to get subs from the two different panels to join using Pixinsight. Possibly because I don't know PI well enough! So the joining of the panels occurred in Photoshop CC.

Joining in PS meant I had to complete all of my color combination and linear processing before joining non-linear panels. I used CCDStack for that, matching the histograms visually so the join would work in PS.

To meet my goal of bringing out the SII structure in the core while allowing the Ha data to support the nebulosity, I had to use pixel math in CCDStack to compress the Ha highlights and reduce the background in the SII. The Luminance channel here is a mean of the compressed Ha and highlights of the SII. That mix was also used for the Red channel. The green used the compressed Ha and OIII. Blue is all OIII.

That was my first time trying to manually compress with pixelmath. My process was to add 1200 and then reduce by the power of 0.7. This kept the shadows constant and matched the highlights to the SII highlights. With the SII I subtracted the mode to reduce the background noise.

2023 EDIT: I always felt there was more to get out of this data. I used the same masters for each panel and this time joined them in PI using gradient merge mosaic. Having joined S, H and O masters allowed me to use a dynamic SHO blend which does lean more on the SII where it is stronger than Ha. BlurX did a better job than my old deconvolution and StarX allowed me to easily process in starless mode while better de-emphasizing the stars later on. Back in those days I did not shot RGB for stars so these are NB stars.

Given that this was all shot at a large image scale (.73") and between 20 and 30 degrees off the horizon, I am looking forward to capturing new data from Chile with the lagoon near the top of the sky.

Original
B
C
Final
D

B

Description: reduced vibrance

Uploaded: ...

C

Description: Complete Re-Edit with BlurX, StarX, NoiseX, a dynamic SHO palate, and 4 more years of experience!

Uploaded: ...

Narrowband imaging

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Status	Advanced success
Started	...
Astrometry.net job	2887420
PixInsight job	VIRWGYC7L4Z1OAVZ4QJJ0XIR1PIUAV0D
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	18h03m52s.284
RA (top/left)	18h07m21s.389
RA (top/right)	18h01m06s.859
RA (bottom/right)	18h00m23s.232
RA (bottom/left)	18h06m38s.320

Dec (center)	-24°17′08″.44
Dec (top/left)	-24°01′46″.30
Dec (top/right)	-23°44′17″.28
Dec (bottom/right)	-24°32′29″.96
Dec (bottom/left)	-24°49′59″.99

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