Trifid Nebula

M20, a nebula in Sagittarius, is known as the Trifid Nebula. Its nebulosity is a combination of both emission and reflection nebulae and also includes a star cluster.

M21, an additional star cluster, appears on the far right.

Taken in suburbia, my light pollution filter seems to enable good contrast and detail for black & white imaging; but in colour (see below) the image appears with a strong blue hue which I have found difficult to reduce without affecting the object itself.


Exposure: 10 x 4 min  ISO 800
Gear: Skywatcher ED120 refractor, 840mm f/l, f/7, Canon EOS 60D. LP filter, no flattener
Location: Leumeah, NSW
Date: 2017-07-18

Object 1:

Messier 20, NGC 6514
Visual magnitude: +6.3
Apparent diameter: 29 x 27 arc-min
Actual diameter: 44 light years
Distance: 5,200 light years

Object 2:

Messier 21, NGC 6531
Visual magnitude: +5.9
Apparent diameter: 14 arc-min
Actual diameter: 16 light years
Distance: 1,200 light years

The processed colour image is not very satisfying:

2017-07-18 M20 Trifid Nebula 5x4min 840mm f7 ISO800dss gnu
2017-07-18: M20 Trifid Nebula 5x4min 840mm f7 ISO800 Colour

Images © R.Powell



  1. Wow, the Trifid Nebula – Mgławica Trójlistna Koniczyna – the superb capture!!!

    Roger, the stellar jet is visible (SW from the nebula’s central star)?
    The radiation from that star makes the jet glow?


  2. Yes, Kazia, to the extent that this is an emission nebula, the glow is due to intense radiation from the newborn stars within. I doubt if there are any jets visible on this image but I could be wrong.


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