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Contains:  Trifid nebula, M 20, NGC 6514
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M20 Trifid Nebula, 


            Barry Brook
M20 Trifid Nebula

M20 Trifid Nebula

Technical card

Resolution: 2032x1420

Dates:Aug. 25, 2014Sept. 2, 2014

Astronomik Ha 12nm 1.25'': 18x600" 2C bin 1x1
ZWO optical ZWO RGBL Filters: 224x300" bin 1x1

Integration: 21.7 hours

Darks: ~70

Flats: ~100

Bias: ~500

Avg. Moon age: 18.44 days

Avg. Moon phase: 25.27%

Bortle Dark-Sky Scale: 6.00

Temperature: 8.00 job: 405181

RA center: 270.590 degrees

DEC center: -23.036 degrees

Pixel scale: 1.543 arcsec/pixel

Orientation: 1.129 degrees

Field radius: 0.531 degrees


A fairly long integration of the reflection (blue) and emission (red) nebula of M20, the fabulous 'Trifid Nebula'. This is a large HII region in Sagittarius, located about 5,200 light years away.

The image was captured a few months ago from my Adelaide surburban backyard, using an Orion ED80T CT apo astrograph (at f/4.8), mounted on an AZ-EQ6. The CCD camera was an Orion StarShoot G3 mono, guided with PHD2 using a think OAG and an ASI120MM-S guide camera. It's taken me a while to dedicate the time required to do the processing!

The image is composed of the following:
Lum = 56 x 5 min
Ha = 18 x 10 min
R, G & B = 56 x 5 min for each channel
Total integration time of 21.7 hours.

I used the Ha data to really make the central emission region stand out above the background. I developed a synthetic luminance channel by blending an exposure-based weighting of the L, Ha, R, G and B luminances. All subs were unbinned.

Captured from late Aug to early Sept 2014, as weather permitted. Pre-processed with flats (light box), bad pixel map (based on 70 darks) and bias in Nebulosity. Aligned and Drizzled in DSS. Post-processed in StarTools.



Barry Brook
License: Attribution Creative Commons

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M20 Trifid Nebula, 


            Barry Brook