Astronomy for RVers
By Chris Fellows, Serenity Mobile Observatory
One of the most common questions I am asked while people look through the telescope is “How do you find this stuff?” The answer to that question is a little complicated because today, with advanced gear and a short alignment procedure, the telescope mount can “find” objects for you.
New astronomers are often frustrated during that alignment procedure because the telescope’s software will ask you to center a bright, named star, in the eyepiece. These are names like Sirius, Capella, Deneb or Arcturus; and if you don’t know which of the possibly thousands of stars that you can see are one of those, then how can you perform the procedure? The short answer is, you can’t. For the purposes of this article I am going to assume no advanced tools, no cell phones, computers, or even a compass. At the conclusion of this series you will be able to walk out into the night with nothing but your senses and orient yourself in space.
At first, learning the names of the stars and how to find them can seem daunting. There are 9,096 stars bright enough to be seen with the naked eye in 88 constellations – those are scary numbers to a prospective new astronomer. The good news is, you don’t need to know anything like that full catalog to find your way around the night sky.
Let’s try to flatten out the learning curve a little. The first fact which should diminish your anxiety is that the stars, from our perspective, seem to be fixed in space relative to each other. They aren’t, of course, but due to the vast distances, the apparent movement over a human lifetime is tiny. What this means in a practical sense is that once you familiarize yourself with the brightest of stars you won’t ever have to “update” that information.
Comfort fact number two is that the 9,096 stars referenced above are of magnitude 6 or higher. Magnitude 6 is the dimmest the unaided human eye can see from the darkest sites. To navigate the night sky you only need to know the 25 or so brightest signpost stars of about magnitude 2 – a much more manageable number. Note that the magnitude scale is a little confusing because the lower the numbers, the brighter the stars.
Thirdly, most of the bright stars are located in easily identified constellations or connect-the-dots pictures in the sky. This makes orientating yourself much easier once you can identify only a few constellations.
OK, with all that out of the way, let’s learn our first and most significant star for us in the northern hemisphere, several of its nearby guide stars, and a few of the constellations. Polaris or “The North Star” is the most important star to learn because it is always in the night sky and the entire universe seems to rotate around it. Polaris is the hub of the great wheel of the night sky and the last star in the handle of the Little Dipper or the constellation Ursa Minor, “the Little Bear.”
A common misconception is that Polaris is the brightest star in the sky. In fact, it is the 48th brightest star in the sky and not as bright as the guide stars we will use to find it. Our first step is to know which way is north. The easiest way to find north is to observe either sunrise or sunset. If you face the sunrise, then you are looking east and north will be 90 degrees to your left. Conversely, if you watch the sunset, looking west, then north is 90 degrees to your right. Make one of these observations (preferably with a glass of wine and a friend) and note the direction of north. Now all we need to do is wait for darkness.
Most people can identify Ursa Major, the Big Bear, but most people also call it “the Big Dipper.” Fewer people are familiar with Cassiopeia, the vain queen in Greek mythology, which to me looks like a big “W” or “M” in the sky depending on the time of night. Let’s suppose it is Ursa Major, the Big Dipper, you spot first; then you can use the two stars on the outside of the “cup” of the dipper, named Dubhe and Merak, to locate Polaris. Just mentally draw a line through them heading north and you should spot Polaris. If it is Cassiopeia you find first, then use the center star of the “W” or “M” called Navi as a pointer to look north to spot Polaris.
Another handy bit of information is Polaris will be a number of degrees above the horizon equal to your Latitude. As I write this article, I am in southern New Mexico, or at Latitude 31.92, so I know if I am looking for Polaris it is about 32 degrees above the horizon.
You now have enough information to find north anywhere in the northern hemisphere, locate and identify three constellations, and locate and name five bright guide stars. Take a few minutes on the next clear night to look north and find these objects. We will build the rest of the night sky off of this foundational information.
Chris Fellows, Serenity Mobile Observatory
Find Chris on Facebook (or, if you’re lucky, at your campground). (Editor: Check out his amazing photos on his Facebook page!)