Well, the winter season for the night sky is ending. Orion, Gemini, Monoceros, Cassiopeia, Perseus, Auriga, and a number of other “Milky Way Halo” constellations are on their way towards setting, and are already past the meridian by the time the sky gets dark enough for any imaging. Until the Milky Way Core comes up in late April and May, it’s Galaxy Season! During the heart of the night, looking up means your looking outwards from the plane of the milky way into deep space. Since there isn’t as much dust and not nearly the same local star density, distant galaxies are much easier to see. There are hundreds, if not many tens of thousands of them out there. There are isolated galaxies, groups of galaxies, chains of galaxies, and whole fields of galaxies.
Unlike some of the nebula I’ve imaged so far, galaxies are a different beast. They are quite dim overall, especially in the city where light pollution wreaks havoc on night sky visibility. While easier to see and image at a dark sky site, they tend to cover much less overall area than your average nebula, with the exception of a few like Andromeda, SMC and LMC, etc. They require longer focal length than I currently have, however with 600mm, and up to 1200mm with a teleconverter, I can still get some decent detail. I gave two groups of galaxies a try over the past week. The first was Leo’s Triplet, a trio of galaxies found in the constellation Leo. Leo is a good region of sky for galaxies, several dozen at least visible to telescopes can be found there, with a good number of major Messier and NGC identified ones. The second was M51, a spiral galaxy and it’s neighbor (perhaps something like our neighboring LMC, Large Magellanic Cloud).
I noticed an interesting thing when I was processing M51. Noise is an ever-present problem when processing astro images, and there are a whole host of techniques to deal with it. One of them involves multiple layers and inverted grayscale layer masks. When I generated an inverted layer mask for M51, I noticed a bunch of additional “fuzzies” that I couldn’t easily see in the normal non-inverted color image:
All of these additional fuzzy objects are galaxies. A total of eight just in this one image. In the wider field around M51, there are dozens more, which span the greater area of Ursa Major (the Big Dipper). I look forward to more imaging during galaxy season. There are some interesting areas, such as Markarian’s Chain in Virgo, a large wide field chain of galaxies that is a fairly amazing sight.