The Galactic Challenge
Galaxies are big. Really big. If you were so inclined to travel to the other side of the Milky Way (and, of course, had the means), it would take you 100,000 years travelling at the speed of light. Yet, due to the massive distance of neighbouring galaxies from our own, these distant objects take up only a tiny fraction of a degree of the night sky, making them very tricky targets to photograph. Such difficulties are magnified (pun intended), as the focal length of your optics decreases. Not only will they occupy a smaller portion of your photograph, but it will be much more difficult to resolve the beautiful fine details of the spirals and patterns within the galaxy. However, I hope to help motivate you to give galaxies your best shot, even if you only have a telephoto lens and star tracker. You don’t need a 2000mm scope and top-of-the-line equatorial mount to get some beautiful galaxy pictures, as the results can still be breath-taking even with a wide, beginner friendly setup!
Picking Your Target
Within this blog post, I will assume that you have something similar to a 200mm (either zoom or prime) telephoto lens, and a star tracker mount. While it is true that with such a setup, your galactic targets will be limited, that’s not to say you can’t take some stunning photos. The first challenge is to pick the right target. The two which stand out as the most beginner friendly are the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33) for their relatively large apparent size. The Andromeda Galaxy takes up a larger portion of the sky than the full moon, in fact! If you’ve tried your hand at Andromeda, or are looking for some of the more niche options, then I can suggest the Pinwheel Galaxy (M101), Bode’s Galaxy (NGC 3031) and the Cigar Galaxy (M81), and the Whirlpool Galaxy (M51). These targets are all small, but are oriented face on (with the exception of the Cigar Galaxy), allowing you the chance to capture the spiral arms and finer details within them.
Imaging Your Galaxy Target
The brilliant part about such a small target is that you don’t need to centre it perfectly, as cropping away even a large portion of the image won’t affect the central feature. That being said, there is something beautiful about a wide angle shot of a galaxy sitting peacefully among a nest of stars. It gives the picture the context and space which it’s so easy to overlook when trying to image a DSO. Just some food for thought! You will need to ensure long enough exposures to capture the fainter details within the galaxy (I try and aim for 2 minutes), and the real test comes with the number of exposures. With such a small target, and such a short focal length, noise can be a serious issue, obscuring much detail if the overall exposure time isn’t satisfactory. For my attempts of the Pinwheel and Bode + Cigar galaxies, I aimed for roughly 4 hours of exposure so that I could get a cropped version of the image with minimal noticeable noise. Obviously, I could have tried for longer, but weather and sleepiness permitting it was the best I could do! The final consideration is light pollution filters. The difficulty here is that city light suppression filters (CLS), and more so ultra-high contrast filters (UHC) cut out broadband light, the very same type of light emitted by galaxies. You won’t be able to get the same contrast with such filters on galaxies as you would on Ha emitting nebulas for example. I still decide to use my filter as it does help cut out some of the unwanted light pollution, but I would certainly recommend experimenting depending on how dark your skies are. I get an unwanted blue hue in some of my images which I struggle to process out, but such are the challenges facing the amateur astrophotographer!
Conclusion
To sum up, pick a target that you can realistically image and get some interesting detail out of, make sure to pile on the exposure time to ensure the most attractive image possible, and experiment with light pollution filters to see what works for you. If nothing else, I hope I’ve given you some inspiration for the Spring galaxy season, and given you some targets to strive for which you might not have otherwise considered. Please do get in touch if you have any topics you’d like me to cover in another blog post! Until the next one, clear skies.
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