M20 the Trifid Nebula (Niall MacNeill)

M20 the Trifid Nebula

After cutting my deep sky teeth on galaxies I thought it was time to image a nebula. I chose one of the most iconic nebulae in the night sky, M20, NGC 6514 or the Trifid Nebula. It is perfectly framed in my C14 EdgeHD/ SBIG 16803 combination.

This is an LRGB image although I have gathered Ha, OIII and SII data try try narrowband processing in due course.

Capture details:

Dates; 2021-04-22 to 2021-05-18

Lights: 16.5 hours integration

Lum: 32 x 600 secs

Red: 23 x 600 secs

Green: 22 x 600 secs

Blue: 22 x 600 secs

Bias: 35

Darks: 35

Flats: 20 per colour channel per camera change

I am indebted to my friends Rodney Watters and Georges Lucotte for their advice on the Starnet process in PixInsight, which allowed me to remove the stars and to process the nebula without messing up the stars or having to play around with masks to protect them. Most advantageous. Merci Georges pour ton aide. C'était très utile mon ami.

I have set up the starless image as a mouse-over as I feel it adds a unique perspective to see the nebula without the star field, although I do love the dense star field of the Milky Way behind the nebula. There are some very bright foreground stars, which I decided not to reduce too much through Morphological Transformation, as compositionally I feel they add a lot to the image. Having said that the bright star at upper right left me with a nasty reflection artefact that need to be dealt with.

My image scale and advantageous latitude, which means the object was at a good altitude throughout the imaging runs, plus generally decent seeing meant that good resolution of detail was possible. I was particularly pleased to resolve the stellar jet as imaged by the HST and, in revisions C & D, I include a zoomed in image of this region and the comparison with the HST image detail. This is a Herbig-Haro object numbered HH 399.

Original
B
C
D
Final
E

B

Description: Starless image

Uploaded: ...

C

Description: Detail of the stellar jet

Uploaded: ...

D

Description: Stellar jet with HST image for comparison

Uploaded: ...

E

Description: Improved star shape. Some of the Lum channel stars were elongated. These were rejected and I then made a Super Luminance, with the good Lum subs plus RGB, before using Kevin Morefield's process in Photoshop, in combination with Starnet, to yield an improved starless image and after further processing a more seamless reintegration of the stars.

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	4931063
PixInsight job	9TQAC8F4PGDB4QVYLJM2ZDMOGAV7QUB1
PixInsight queue size	n/a
PixInsight stage	n/a

RA (center)	18h02m32s.760
RA (top/left)	18h03m38s.474
RA (top/right)	18h01m27s.304
RA (bottom/right)	18h01m25s.591
RA (bottom/left)	18h03m37s.332

Dec (center)	-22°57′50″.85
Dec (top/left)	-22°42′23″.85
Dec (top/right)	-22°42′07″.22
Dec (bottom/right)	-23°13′15″.10
Dec (bottom/left)	-23°13′35″.98

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