A Favorite DSO
Do you have a favorite deep sky object (DSO)? I thought about this after filling out the recent LCAS on-line observing preference survey. I think many of us might choose some spectacular object like M42 ("Orion Nebula"), M31 ("Andromeda Galaxy"), or M51 ("Whirlpool Galaxy"). But I would find it hard to pick a favorite among all the interesting objects in deep space. So I guess if I had to choose anything it might be M83.
What's so special about it? Well, there are a lot more spectacular objects. But good old M83 has endeared itself to me simply because it's the final object I found in my quest to log all the Messier objects. Sometimes it's not just the object itself that is imprinted on our mind, but the flood of other memories that it engenders. In the case of M83, it was the struggle to find it that I most recall and the places from which I tried to observe it.
First, a little bit about M83. It's a large almost face-on spi-ral galaxy in Hydra. It's listed at magnitude 7.5, so you'd think it would be easy to see. But because it is so large (11.2'x10.2'), its light is spread across a wide swath, giving it a surface brightness of around 12.8. On top of that, its position in the constellation Hydra ensures that it never gets very high in our sky, so is afflicted by light pollution and atmospheric extinction. But in high resolution photos, it is a beautiful galaxy.
I had started on the quest to locate all the Messier objects as a young teen back in 1955. Through a number of differ-ent telescopes and observing fits and starts, by the early 1980s I was wrapping up the final few Messier objects. The last holdout was M83, which I pursued from my back-yard in Libertyville. The sky there was much better than it is now - I regularly did deep sky observing. By the time we moved away in 2003, only the very brightest DSOs were visible, and not very well at that. As we all know, it's the toll of light pollution. On top of that, trees had grown up, so there wasn't much sky to be seen.
I did try for M83 at a number of other sites. Perhaps the most memorable one was in early spring 1985 at an Astro-nomical League conference at Fermilab in Batavia, de-voted to plans for the coming apparition of Comet Halley in 1986. One activity that day on the Fermilab tour was a stop at an ion chamber which recorded incoming solar par-ticles. A look into the dark chamber showed many flashes of light, indicating an especially active sun. That night an area to the north of Wilson Hall had been set aside for us to set up telescopes. I had brought my 8-inch Newtonian and because of the good horizon, I thought there was a chance I could see M83 even though it was still pretty low in the sky and there was some light pollution. Despite my best efforts, the galaxy still eluded me. However, our at-tentions were eventually diverted by a beautiful display of northern lights. (Remember the active ion chamber?) We even watched the aurora from inside our cars all during the trip back home to Lake County.
Then with a clear night on May 17, 1985, a few of us headed out to the dark skies of Apple River Canyon state park near Galena, Illinois. This would be the best opportu-nity yet, so M83 was my first target of the night. And ... bingo ... I scored it right away. All it took was a dark sky and clear horizon. And it was gorgeous, with spiral arms and a bright central hub easily visible.
We don't observe from Apple River Canyon state park anymore. The sky is still dark out that way, but young trees planted in the campground have over the years grown up and now obscure much of the sky. However, there are many fond memories of time spent there under the stars. These are recollections that never get recorded in an ob-serving log, but the human memory in many cases makes up for the lack of a written record. In that respect, M83 is a memory jogger. I'll bet many of you can think of other objects with a similar fondness.Published in the July 2009 issue of the NightTimes