Image Image Image Image Image Image Image Image Image Image

View from a Scope | July 25, 2021

Scroll to top


No Comments

Lost in Triangulum?

Lost in Triangulum?

The Triangulum Galaxy is a spiral galaxy approximately 3 million light years from Earth. This Galaxy is a member of our own local group of Galaxies which include the The Milky Way, Andromeda and about 30 other smaller galaxies. On a very clear night with dark skies you could just about make it out, making it one of the most distant objects you can see with the naked eye.

Where is it?

The Triangulum Galaxy gets its name because of its proximity to the Triangulum Constellation. this constellation is primarily made up of 3 stars forming (yes you guessed it) a triangle. To find the Triangulum Galaxy draw an imaginary line between the long point of this triangle of stars and the star Mirach, which is the brightest star just beneath Andromeda. About 1/3 of the way up this line lies Triangulum. This time of year (Sept – Dec) is an ideal time to view Triangulum as it sits at nice height to the south around 1 or 2 in the morning (UK time)



As mentioned earlier you will require exceptional viewing conditions to see this with the naked eye. However through a 4″ / 6″ telescope on a clear night you should be able to make out its structure. Remember to give yourself sometime to allow your eyes to adjust and you will be amazed at the detail you can see.

Whats in it?

With a diameter of about 50,000 light years the Triangulum galaxy is the third largest member of our local group of galaxies. It may be gravitationally bound with Andromeda. It is estimated that Triangulum is home to around 40 billion stars, compared to the 400 billion stars of the Milky Way and the 1 Trillion stars of the Andromeda galaxy.

How to Photograph Triangulum?

In order to photograph the Triangulum galaxy you will need, as mentioned above a number of times very clear skies. As the Triangulum is a diffuse Galaxy (no well defined boundaries) it is strongly affected by small amounts of light pollution.

In terms of your camera settings for a DSLR which is what I use, you will need to have a

  • High ISO (Measure of the Cameras sensitivity to light), Mine only goes to 1600 but 3200 would be better. (Although note that higher ISO introduces more noise into your image)
  • Aperture or F number needs to be set as low as possible, Mine was set to F3.5
  • Exposure time, The exposure time is the key  factor. This determines how long the camera is to image the object, There are a lot of factors that will determine how long you can expose for which I will go into more detail on in another post. Seeing as I was using a guided mount(One that tracks the stars accurately) I was able to expose for longer in my case 5 minutes. An unguided mount (which has been polar aligned) would only really be able to expose for about 30 seconds.

When taking the photo as mentioned above exposure is key, a guided mount is really necessary in order to bring out the real detail in the galaxy, but there are ways around this as well. A free program called Deep Sky Stacker will allow you to combine multiple images and it will build a longer exposed image out of these. i.e. 10 x 30sec images via Deep Sky Stacker = 1 x 300sec image.

This allows for far more detail to be brought out than would be possible with a single 30 sec image. However a guided 300 sec exposure will always give you more detail than a stacked 300 sec exposure.

In my case because my guided setup is good not great I limited my exposures to 5 minutes, but I took a number of these and applied them to Deep Sky Stacker, and with some processing in this program and in Photoshop I was able to produce the image at the top of this post.

At a later date i will write a post detailing the processing techniques possible in Deep Sky Stacker as well as my own methods for processing in Photoshop.

We are now coming into a great time of year for viewing these Galaxies, both Andromeda and Triangulum are ideally placed in the southern skies and the nights are starting to get longer.


Submit a Comment