April Skywatch

I’ve promised a column on some telescope basics, and as the evenings start to warm up it’s finally time to deliver. Maybe you’re interested in more stargazing than casual naked-eye observations from your back porch, but you’re unsure of where to begin. Sometimes the options for purchasing a good starter telescope seem quite daunting. Where to begin? What type should I get? Which mounting is best? How do I avoid a cheap dud?

This month, I’ll offer a few pointers on choosing and getting started using a telescope for some basic backyard observations. As I’ve mentioned before, I focus on observing objects that you don’t need to be in perfectly dark skies to see. My own stargazing takes place in the city limits of Kankakee, with streetlights, trees, and the occasional porchlight marring the view. With a little knowledge and patience though, even a city sky can be a treasure trove.

Of course, it all starts with a good telescope. When I was preparing to purchase a new set of telescopes for my astronomy labs at Olivet several years ago, I asked the members of the Kankakee Area Stargazers for advice. I wanted instruments that were high quality but relatively inexpensive, easy to use and train students to use, and resilient enough that I wouldn’t worry about them being easily damaged The scope most recommended was a basic 6-inch Dobsonian reflector from Orion Telescopes. I purchased a small fleet of these instruments for student use and have had no regrets. They are simple, durable, and offer great viewing.

So what exactly is a 6-inch Dobsonian reflecting telescope? We’ll start with “reflecting.” Telescopes come in two basic types: reflectors, which use mirrors to gather light, and refractors, which use lenses. If you walked into Wal-Mart for a cheap telescope, you’d almost certainly be buying a refractor. Though there certainly are many refractors that are very high quality, you’re not going to get one like that at Wal-Mart. For a real quality refracting telescope, you would be spending several times more than you would for a reflecting telescope of similar size. If you’re looking for a serious but affordable starting instrument, stay away from refractors and start with a good reflector.

The next question is regarding aperture or (in simple terms) size. Generally speaking, the larger the diameter of a telescope, the better view you’ll have of objects. But also generally speaking, larger aperture also means larger price. Six inches offers enough light-gathering power to easily showcase Saturn’s rings or the moons Jupiter, hone in on the Moon’s craters, or (in dark skies) reveal distant nebulae and galaxies.

Next, you need to consider how the telescope is mounted. As it turns out, pointing and holding the telescope steady is one of the most important parts of getting good views (and not getting incredibly frustrated). There are lots of different ways to mount a telescope, but the type known as a Dobsonian mounting is the sturdiest and easiest that I’ve worked with. A Dobsonian mount makes it very easy to point the telescope to an object in the sky (especially if you spring for a simple laser-finder) and to keep the object in sight and steady once found. And if you’re observing with students or young kids, having a telescope that is on a steady and solid mounting is crucial.

Once you have your telescope picked out, the second step is to get a handful of eyepieces to use with it. Eyepieces magnify the image of the telescope, with the general rule that for a specific instrument smaller eyepiece focal length yields higher magnification. If you’re looking at large objects like the Moon or star clusters, you’ll want to use an eyepiece with a longer focal length (e.g., 25 mm). Then, when you want to zoom in on lunar features or try to split very tight double stars, you use an eyepiece with a shorter focal length to magnify the view. Most telescopes come with two or three eyepieces, and this is usually plenty for the beginner.

Finally, you need to know how to find the objects in the sky you want to view. I tend to eschew computerized mounts that point the telescope for you or tell you where to point it, because I think part of the fun is becoming familiar with the night sky yourself. But you’ll need some good resources to get you started. A quality star atlas is a must (I use the Cambridge Double Star Atlas), but it’s not much to go on if you’re just beginning. I’ve found James Mullaney’s Celestial Harvest to be an excellent guide to highlights in each constellation, and a tool like Guy Ottewell’s Astronomical Calendar (which unfortunately won’t be published after this year) lets you know what planets and constellations to spot when.

Then comes patience. Wait for clear nights and determine what constellations will be overhead. Do a bit of reading before you head out (or take a red flashlight with you to read at the telescope) and simply try to become familiar with the objects in one or two constellations at a time. Don’t feel like you need to learn the entire sky immediately. This month, for instance, Leo is a great place to start, from the lovely double star Algieba in the Sickle of Leo’s mane, to Jupiter and its moons just below the constellation (always a wonderful sight to start with), to the sweep of galaxies beyond Leo’s tail (though you’ll need to get away from the city lights to really appreciate these).

You’ll be amazed at what passes over your head each evening, generally unappreciated and unobserved, but within reach with a simple, good instrument.

This column first appeared in the Kankakee Daily Journal.


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