M20 - THE TRIFID NEBULA - DSLR vs CMOS Astrophotography

Updated: Oct 28, 2019

Messier 20 is a great target for amateur astrophotographers, no matter which instrument you own. A close-up image will show a lot of details, especially in Barnard 85, the dark nebula.

A wide shot will allow you to capture both M20 and M8 in the same frame. Both are about the same magnitude and make for an impressive photo together.

Messier 20 is not very common. The Trifid Nebula, and the stars that burn in the gases are probably the youngest of our galaxy. Two red and blue areas show the gas surrounding the birth of new burning stars.

We have imaged Messier 20 with both our old Canon t3i DSLR camera and, more recently, our ZWO ASI 1600MM-Pro CMOS camera. We will show you the comparison between both in this post!

We also have a full episode about M20 (and M8) on our YouTube Channel.

We first imaged this nebula three years ago, with our Canon t3i. You can see the result below.

Sadly, this unmodified DSLR camera is not great for bringing out the Hydrogen Alpha gases, so the red area doesn't show as much as we were hoping it would. 

To the bottom right, you can see the cluster of stars Messier 21 as well. That's 2 Messier objects in one frame!


Camera: Canon t3i

Telescope: Orion 8" Astrograph f/3.9

Mount: Atlas EQ-G motorized Mount

Coma: Baader MPCC Coma Corrector MkIII (screwed improperly!)

Guiding: Starshoot Autoguider - 50mm Guide Scope

Processing: Pixinsight


Total Exposure Time: 3 hours

Exposure Time per frame: 3 minutes

60 lights - 21 Darks - 20 Bias

ISO: 400

3 years passed by, and we decided to revisit this target with a wider telescope and our new CMOS camera. Here is the result with the ASI 1600MM-pro cooled Astrophotography camera. We actually prefer the image we got with our Canon t3i, mostly because the one below lacks a lot of detail in the second blob. Perhaps we should have spent a little more time with the Oxygen III filter? You will also notice that some of the stars are a bit too pink and maybe oversaturated.


Camera: ZWO ASI 1600mm Pro Mono

Telescope: Meade 70mm APO Astrograph

Mount: Atlas EQ-G motorized Mount

Guiding: ZWO ASI 290MM Mini

Acquisition: ZWO ASIAIR

Power: Pegasus Astro Pocket Powerbox

Processing: Pixinsight


Total Exposure Time: 3 hours

Exposure Time per frame: 3 minutes

Filters: Ha (1 hour) / SII (1 hour) / OIII (1 hour)

Gain: 139

Locating the Trifid Nebula

M20 is located just above the Lagoon nebula, in the Milky Way band. To find it, you can simply follow the same steps as for Messier 8, but this time, head just a bit higher.

Messier 20 is smaller than its neighbor and will be relatively easy to spot with binoculars, but seeing it with the naked eye is more of a guessing game. It will look more like a fuzzy star than a gray patch.

Once again, do not wait until the last minute to capture this nebula, as it does not rise very high.

You may also see Messier 21 through binoculars or a telescope. M21 is a star cluster that is near to the Lagoon!

  • Dark nebula in front appears to separate the two blobs

  • Photographed by Hubble in 1997

  • Brightest star is a triple star system


Below you can see our single shots of M20.

The first image (in color) was taken using our unmodified Canon t3i DSLR Camera. It looks really good for just 3 minutes of exposure, and the colors are really popping already!

The three other ones are, in order, 3 minutes with an Ha, SII and OIII filter. M20 can be seen on the top right of each narrowband image. The nebula in the center of the frame is M8, the Lagoon Nebula, which we imaged at the same time.

Just like M8, M20 doesn’t get very high from the horizon. This can be challenging when photographing it because you want to make sure that there are no big cities in the direction of the nebula, or it will create a light pollution dome that you will have to shoot through.

Make sure to make Barnard 85, the black nebulosity, visible in front of the beautiful reds and blue of M20.

One of the collimating screws on the telescope broke right before the imaging session with our Canon t3i, and we feel like the stars around aren't as sharp because of that (even though we did our best to collimate perfectly with 2 screws).

Either that or our coma corrector wasn't screwed on properly.

On the right is a cropped image of the star cluster M21. As you can see, it was near the edge of our photo so it was affected by the coma/collimation problem. It is still not bad though.


In Episode 13, we try out a wide telescope, the Meade 70mm APO Astrograph, and photograph both Messier 8 and Messier 20 in the same frame! Watch it below to see how we ended up with our final image.


The Trifid Nebula is a colorful target that is easy to photograph for anyone! We are glad we were able to revisit this target with a cooled astrophotography camera, even though we wish both "blobs" of gas were visible.

Make sure to follow us on Facebook, Instagram, and YouTube to stay up to date with our work!

Clear Skies,

Galactic Hunter

Part of: The Astrophotographer's Guidebook

Description: Discover 60 Deep Sky Objects that will considerably improve your Imaging and Processing skills! Whether you are a beginner, intermediate, or advanced astrophotographer, this detailed book of the best deep sky objects will serve as a personal guide for years to come! Discover which star clusters, nebulae, and galaxies are the easiest and most impressive to photograph for each season. Learn how to find each object in the night sky, and read our recommendations on imaging them in a quick and comprehensive way. Each target in this guide contains our advice on imaging, photos of expected results, and a useful information table. We've also included a few cool facts about each target, a map to find it in the night sky, and more!

#astronomy #astrophotography #messiercatalog #messier #galaxy #nebula #cluster #stars #space #galactichunter #nevada #lasvegas #canon #orion #telescope #m20 #trifid #trifidnebula #ASI1600mm #m8

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