The Joy of Double Stars

My mother says that when I was a child, I would go on learning jags. I'd get obsessed with one subject, learn everything I could about it, and then go on to another. My stargazing career is a bit like that too — especially when I'm observing near my city home.

A decade ago, I was obsessed with observing all the Messier objects. This culminated in my online Urban and Suburban Messier Guide, a project that I finished before I started working at S&T. That project required obsession, because observing all the Messier objects from light-polluted surroundings requires lots of effort and concentration. I would often drive 45 minutes to my astronomy club's observing field, spend hours at the telescope, and return home exhausted in the small hours of the morning.

As Jeremy Perez's sketch of Gamma Leonis shows, each component of the double star is surrounded by diffraction rings when the atmospheric conditions are steady. See Jeremy's website for more of his amazing sketches.
Jeremy Perez
These days, I find short, frequent observing sessions more enjoyable than occasional, long, strenuous ones. Fortunately, there's an essentially inexhaustible supply of suitable targets. Unlike deep-sky objects, double stars are usually easy to find and observe. By analogy with hiking, my other favorite activity, a deep-sky object is like a mountaintop; it has a lot to offer, and once you've made the effort to get there, you want to spend a while. Double stars are like the stops on a nature trail. I linger at each one for just a minute or two, and then move on to the next. Deep-sky objects have many details to explore. With a double star, I just note the separation, the position angle, the relative brightnesses, the colors, and my overall impression — and that's really all there is to say.

The other beauty of double stars is that I don't have to travel far to see them. Thousands are visible and splittable even through small telescopes in the middle of a city. The Moon doesn't hurt them a bit, and they can even be viewed through thin clouds — which is just as well, considering the fickle weather we've been having recently.

I write more about double stars and the resources that I use to find them next week, or whenever I get a free moment. Bye 'til then.

2 thoughts on “The Joy of Double Stars

  1. Jeff Gortatowsky

    If you can see just a few stars naked eye from a light polluted backyard, you can hop to doubles. It requires a 50mm or 60mm finder scope but you can do it. In my case I use a 10cm f/5.4 telescope and very low power. That way I can use the scope as the finder scope. Using an equatorial mount helps as well as directions are obvious. Directions are important when you have fewer stars to hop by. When you arrive at your target, unlike the DSOs that will be invisible, the double will show through. To me that is why I like to observe doubles, it’s astronomy that can be done almost anywhere.

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