M33 - The Triangulum Galaxy - Astrophotography

Mis à jour : janv. 20

The Triangulum Galaxy is a bright spiral galaxy in the constellation Triangulum. It is one of the most popular objects for beginner amateur astrophotographers.

Object Designation: M33

Also known as: The Triangulum Galaxy

Constellation: Triangulum

Object type: Spiral Galaxy

Distance: 2,300,000 light-years away

Magnitude: 5.7

Discovered in: 1764

Like the Andromeda Galaxy, the Triangulum Galaxy is visible with the naked eye, in extremely dark skies far from any light pollution. As we explained in Episode 4 of Galactic Hunter, the Andromeda galaxy is doomed to crash with our own, the Milky Way. M33's fate is no better. The Triangulum galaxy will get stuck in the gravitational pull of the impact, and orbit the new Milkomeda until finally crashing into it. In the end, our Milky Way, the Andromeda galaxy, and the Triangulum galaxy... will only be one.

M33 is the second apparent largest, and brightest galaxy to photograph in the night sky. 

The Triangulum galaxy fits perfectly in a telescope that has a focal length of 800mm (see photos below) and a good result can be achieved with just 1-3 hours of exposure depending on the camera. We recommend doing 5+ minute exposures in order to capture faint details, including the huge NGC 604 in one of the spiral arms of M33.

The Triangulum Galaxy with a cooled One-Shot-Color camera

July 20, 2020

Almost four years later, in July of 2020, we took a trip to Landers, CA to visit the OPTeam. You can watch our fun video about that weekend HERE.

Landers has a very similar light pollution level as our usual imaging spot from our first attempt (Bortle 3 to Bortle 4) and we used the exact same telescope to capture Messier 33 again!

The main difference here was the camera. Instead of using our Canon 7D Mark II DSLR camera, we used the QHY128C which is a cooled One-Shot-Color camera. We unboxed and reviewed this camera on our YouTube channel and show you a lot of images taken with it!

We did not process the data for a while, as we only had a few frames on that target. We decided to take a few more from our usual imaging location when we were back in Las Vegas. We recorded that part for the Galactic Course, where the second segment of Season 1 is all about imaging a galaxy with a reflector telescope and a cooled One-Shot-Color camera!

As you can see on the image below, the result is fantastic! What blew my mind is the fact that this was only 70 minutes of total exposure, while our image with a DSLR camera was more than 3 hours!


Camera: QHYCCD 128C

Telescope: Orion 8" Astrograph f/3.9

Mount: Software Bisque Paramount MyT

Guiding: ZWO ASI 290MM Mini

Processing: Pixinsight


Total Exposure Time: 1 hours and 10 minutes

Exposure Time per frame: 600 seconds

Filters: ZWO IR Cut Filter

Gain: 3200

I processed this data using the workflow described in our basic PixInsight Processing Guide, which is available for download! Make sure to check out our Advanced version as well!

Want to learn all aspects of astrophotography in the most efficient way possible?

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The Triangulum Galaxy with an unmodified DSLR camera

November 2016

In 2016, we imaged Messier 33 with our new unmodified DSLR camera: the Canon 7D Mark II. We spent three hours capturing this object from a Bortle 4 zone and, on the same night, recorded Episode 5 of Galactic Hunter! Make sure to watch the video to see exactly how we imaged this target from start to finish!


Camera: Canon 7D Mark II

Telescope: Orion 8" Astrograph f/3.9

Mount: Atlas EQ-G motorized Mount

Coma: Baader MPCC Coma Corrector MkIII

Guiding: Starshoot Autoguider - 50mm Guide Scope

Processing: Pixinsight


Total Exposure Time: 3.1 hours

Exposure Time per frame: 6 minutes

31 lights - 15 Darks - 15 Bias

ISO: 800

How to find the Triangulum Galaxy

The Triangulum galaxy lies in the Triangulum constellation. The problem is, the Triangulum constellation is pretty dim, and using the Andromeda constellation, or Pegasus, to find the galaxy is the easier option.

As we said earlier, the Triangulum galaxy can be spotted with the naked eye, in extremely dark skies, far from any light pollution.

The easiest way to locate Messier 33 is to first find the Andromeda Galaxy (red oval shape on top right of map above). Once you have M31 on your sight, notice the distance between the galaxy and the star Mirach, and match that distance on the opposite side of this bright star.

Even under very dark skies, the galaxy is difficult to see with the unaided eye, but a pair of binoculars will easily reveal a blurry patch of light in the sky. Using a telescope will allow you to see the core, and make out some details within the arms.

Wide-field Astrophotography of Messier 33

Although not as impressive as M31, M42, or M45, the Triangulum galaxy is still a good target for wide field photography.

Make sure to click on each picture to get a better view! You can easily see the shape of the Triangulum galaxy, with the bright core and beautiful spiral arms!

On the left is our photo of both the Andromeda Galaxy (right, middle) and the Triangulum Galaxy (left, bottom), in the same frame using a 50mm lens. We spent 4 hours on the imaging, with our good old Canon t3i attached to an iOptron Skytracker.

This second image (right) is a cropped version of M33, taken from the full wide field photo but using a different processing method (Although it seems like I forgot to use SCNR during the processing workflow to take off the green color).


Camera: Canon T3i (600D)

Lens: Canon 50mm f/1.8

Mount: iOptron Skytracker

Processing: Pixinsight


Total Exposure Time: 4 hours

ISO: 800

Single Shot & Processing of M33

When talking about processing, the Triangulum Galaxy has a similar difficulty level to the Andromeda Galaxy, although if you have already imaged and processed M31 with an 8" or bigger telescope, you will find M33 to be a little easier.

This time, the galaxy is not too large that you can easily distinguish the dark sky with the nebulosity, making your background neutralization tasks much less tricky than with M31. The key here is to get as much of the arms as possible, without overdoing it. As you can see in our main image, each arm is pretty well revealed, but pushing the software a little more would have made some bright, non existent haze visible just around the galaxy. 

Below is what a 6-minute single shot of the target looks like with our unmodified DSLR camera. You can see a lot of details around the core, but not so much in the spiral arms. This changes once you stack everything!


When staring at our main photo of the Triangulum Galaxy, I wondered what that white little patch was in one of the arms. I thought it was a blown out part from the processing, until I did some research and realized it was NGC 604: One of the largest nebulae in our entire local group! To give you an idea of its size, it is 40 times the size of the Orion Nebula... 

Below you can see our cropped photo of M33, with Hubble's image of NGC 604 where the nebula is located.


The Triangulum Galaxy was the winner of Episode's #4 votes, so it was in the center of the fifth episode of Galactic Hunter!

Final Thoughts

To conclude, The Triangulum Galaxy is one of the most impressive galaxies in the night sky. It is a great target for beginners, and we would recommend you give it a go after having imaged the easy trio (M45, M42, M31). Make sure to spend enough time on it, and do not overdo the processing! You can also give this target a go at wide field photography, just make sure to include the Andromeda Galaxy if using a 50mm lens or smaller.

Clear Skies,

Antoine & Dalia Grelin

Galactic Hunter


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!

The Astrophotographer's Journal

Description: The Astrophotographer’s Journal is a portable notebook created for the purpose of recording observations, cataloguing photographs, and writing down the wonderful memories created by this hobby. This book contains more than 200 pages to memorialize your stargazing and imaging sessions, as well as a useful chart on the last pages to index exciting or important notes. Read back on the logs to see how much progress you have made through the months, the problems you overcame, and the notes taken to improve in the future. Just as the pioneers of astronomy did in their time, look up and take notes of your observations as you are the author of this star-filled journey.

The Constellations Handbook

Description: The Constellations Handbook is a logical guide to learning the 88 constellations. Learning the constellations is difficult. Remembering them is even harder. Have you ever wanted to look up to the night sky, name any pattern of stars and be able to tell their stories?This book groups the constellations in a logical order, so that the reader can easily learn them by their origin, and see how their stories interact with one another as a group.The last pages of this book include an index of all 88 constellations, each with a slot where you can write your own personal tips and tricks in order to memorize them with ease.The Constellations Handbook is not just another guide listing all the constellations from A to Z and their location, it is the perfect companion for stargazing, and a learning journey through the ages.

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