In my very first post earlier this month I talked about astronomers who work their way methodically through object lists, often to the detriment of the object. A quick glance, a note or two, maybe a quick sketch and then they are off to the next object. All well and fine if you are looking at 14th magnitude galaxies, but if your list is packed with the brightest deep sky gems, what is the hurry? 400 top objects could well last your entire life.
To make certain that I never finish my life list, or run out of options on any given clear night, I chose the NGC list a long time ago as my main deep sky emphasis. I will not pass a Collinder or Berkeley cluster without a look, but my longest viewing time is spent on the NGC list. In a lifetime of observing I have only seen about 630 of them, averaging just over one per observing session (last night I logged two new ones). I really need to ramp that up a wee bit if I want to see all available from my latitude before I die.
The new edition of Uranometria 2000 claims that more than 30,000 non-stellar objects are on its charts. That's over 22,000 more than are in the NGC list. Good grief. Makes me kind of thankful that I am not overly obsessed. Of those 30,000 objects, nearly 26,000 of them are galaxies. Which means that nearly 5 in 6 non-stellar objects viewable in the night sky with amateur scopes are galaxies. Most of those are pretty faint, too. Here is the breakdown, as reported on the atlas' back cover:
25,883 galaxies
671 galaxy clusters (Abell)
14 star clouds
1,613 open clusters, including those in the Magellanic Clouds
170 globular clusters
355 bright nebulae
367 dark nebulae
1,145 planetary nebulae
260 radio sources
35 x-ray sources
I remember being very surprised when I first learned how many galaxies were available to amateur astronomers (all the ones listed in Uranometria are mag. 15 or brighter). I mean that I was very surprised. Growing up loving the Milky Way area and all of its clusters and nebulae, it was easy to conclude that clusters of stars far outnumber galaxies. That, to say the least, was an erroneous conclusion. If one decides to choose the NGC for a life list, one must be prepared to see some galaxies. I don't just mean the ones in the Messier catalogue, either.
Finding and doing justice to galaxies requires the very finest of dark skies. I used to be able to pick off 12th mag. galaxies from my back deck with my 8" scope. Light pollution has increased so much in my area that this is now quite impossible. I did snag one last night with the 12", but if I want to do a decent job of observing in Leo this spring, I have to be prepared to travel with the scope. This brings on an interesting conundrum. I also had a preliminary look last night at M 65 and M 66, bright galaxies in Leo. Compared to faint little eg 2894 viewed previously, they were pretty darn impressive. So, do I observe the brighter galaxies from my home, saving the fainter ones for country skies? Though this is a feasible plan, I try to imagine what eg 2894 might look like from a dark sky. If I can even see it from home, then it might just be that much more impressive from a dark sky. Should I save all my faint objects for darker skies? What about M 65 and M 66? Of the two, M 65 was less bright but it was really huge after viewing it for a few moments. M 66 was quite bright, and I could probably have used up to 300x without any loss of brightness. However, what would these objects look like from a really dark sky site?
One solution to this problem, which I'm certain many of us face all too often, is to keep notes and report on the brighter ones as seen from home suburban skies, but also return to them in dark skies and enjoy a quick peek. eg 2894 seemed to have a little cluster of very faint stars superimposed over it, only barely resolvable at high power with averted vision. Was there a stellar core? Couldn't really tell. But the elongated galaxy could be seen in behind the star field, best at 150x in the 12". I know I want another look in darker skies, resolving those faint stars more easily and perhaps seeing some detail in the galaxy itself.
Whereas fainter galaxies pose severe problems for suburban viewers, objects such as clusters and nebulae, especially planetary (I also enjoyed good views of pn 2346 in Monoceros last night), do not pose significant problems. And double star work can carry on quite well, too, often even during full moon nights. However, I am determined to do as much deep sky work in the darkest skies I can reach. I've been spoiled by my northern Ontario early years of observing. Another time I will talk about my nearby observing options, and how they may best be used. Until then, I hope you enjoy a clear sky night or two.
Mapman Mike
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