The Triangulum Galaxy is located in the small constellation of Triangulum, a little way south of the large and better known Andromeda Galaxy. It is the third largest spiral galaxy in our small local cluster, at about half the diameter of the Andromeda Galaxy and our own Milky Way. At a distance of 2.7 million light years it is a little further away than Andromeda and is the most distant object that can be seen with the naked eye – but only under excellent viewing conditions.
The galaxy was probably discovered in 1654 by Italian astronomer Giovanni Battista Hodierna, but was later re-discovered by Charles Messier in 1764 and included in his catalogue as M33. Towards the end of the 18th Century, William Herschel studied the galaxy and allocated four areas of bright Hydrogen nebula their own NGC designation. The largest and brightest being NGC604 (located above right of the core in the image above). This is one of the largest Hydrogen gas clouds known at about 1500 light years across. In 1850, Lord Rosse identified the spiral nature of the galaxy – one of the first spiral galaxies to be classified.
Measurements of its location and movement suggests that the Triangulum Galaxy is gravitationally bound to the Andromeda Galaxy and indeed may have interacted with it in the past. It is likely that within the next 2.5 to 5 billion years it will collide and merge with Andromeda, probably also participating in the merger of Andromeda and the Milky Way into a single large galaxy.
I first attempted to photograph Triangulum towards the end of 2023, but did not think I had enough data to process the image properly. Therefore when the galaxy came around again at the end of 2024, I gathered more data to add to the original set. This is the first time I have combined data taken at widely separated times, and it appears to have worked – the final image being better than either set of data processed individually. This is an LRGB image, with Luminance data gathered to provide the detail, then Red, Green and Blue filter used to provide the colour elements. The individual sub-exposures were stacked in Deep Sky Stacker, then processed in PixInsight, with a few minor tweaks in Photoshop at the end.
Image Details
- Date: 13th December 2023 & 27th November 2024.
- Telescope: Altair Astro 72EDF. Focal Length: 432mm, Aperture: F6.
- Camera: Altair Astro 183MM Cooled Mono Astro Camera. Offset 40, Temp -10degC. Gain 100 for original L-Pro data, 400 for original Colour data, 200 for all later data.
- Filters: Luminance: Optolong L-Pro. RGB – Optolong RGB Filters.
- Mount: Skywatcher HEQ5.
- Guide Scope: Altair Astro 60mm.
- Guide Camera: QHY5LII.
- Exposure Details: L: 54 x 60s + 72 x 80s (2hr 30min), R: 26 x 60s + 21 x 120s (68min), G: 26 x 60s + 14 x 120s (54min), B: 22 x 60s + 20 x 120s (62min).
- Total Integration Time: 5hr 34min.