Stargazer stocking stuffers: Holiday gift guide
Is there an amateur astronomer on your holiday shopping list? There are plenty of great gifts you can give them without breaking the bank.
Wed, Dec 12, 2012 at 08:00 AM
If there's a stargazer on your holiday shopping list, we're here to help. And you don't need to break the bank to find the perfect gift — we've compiled a list of great options, all priced under $60:
When most beginners think of astronomy, they think of telescopes. But serious sky viewers, although they may own one or more telescopes, are almost never without a pair of binoculars. Binoculars are useful in their own right, as a tool for casual observing of large swaths of sky, such as found in the Milky Way, and for viewing large astronomical objects like the Pleiades star cluster and the Andromeda Galaxy.
The most useful size of binoculars for astronomy are 7x50 and 10x50. Binoculars are described by two numbers, magnification and diameter of objectives (main lenses). So these are binoculars magnifying either seven times or 10 times, and with main lenses 50 mm in diameter. Their low magnification allows them to be handheld steadily by most people, and their 50 mm lenses gather enough light to show astronomical objects well.
What about more powerful binoculars, such as 15x70 or 20x80? These can give spectacular views, but they are not as light in weight or user-friendly as 7x50 or 10x50. Remember that binoculars have to be held above your head, and heavy binoculars get very tiring very fast. These higher magnifications require being mounted on a tripod, which makes them less convenient than smaller binoculars. [Review: Best Binoculars for 2013]
Avoid binoculars that have ruby coatings, zoom magnification, or "universal focus"; these are gimmicks that don't work well for astronomy. Look for binoculars that are fully multicoated and have BaK-4 prisms, rather than the BK-7 prisms found in cheaper binoculars.
Binoculars are also an essential aid in finding faint objects with a telescope. You use binoculars to plan out the route you will follow to "starhop" to the next object you want to view. A few minutes locating an object in binoculars will save half an hour of backbreaking agony at the telescope's finder.
Eyepieces are small magnifying glasses placed on a telescope to obtain different magnifications. Many beginners mistakenly call these "lenses" because they resemble camera lenses. Most telescopes come with one or two eyepieces, which are enough to get you started, but soon, you will want a wider field of view or more magnification.
Magnification is calculated by dividing the focal length of the telescope (typically 900 mm to 1200 mm) by the focal length of the eyepiece (typically 40 mm to 4 mm). [Best Telescopes for Beginners]
The most common eyepieces have focal lengths of 25 mm or 20 mm and provide low magnification with a fairly wide field of view. If you want more magnification, you need a shorter focal length eyepiece — typically with a 10 mm to 5 mm focal length.
But be careful about how much magnification you use, because all telescopes are limited by the laws of physics in the magnification they are capable of. As soon as you reach a magnification equal to the diameter of the telescope's objective in millimeters, you reach the point of diminishing returns. You may make the target larger, but it won't get any sharper; in fact, it will start to appear fuzzier. So, don't go above 75x with a 75 mm telescope, or above 150x with a 150 mm telescope.
Telescopes are often advertised with magnifications higher than these limits, but purchasers discover that these high magnifications are in fact useless. That's why we always recommend avoiding buying a telescope advertised by its magnification.
Most astronomical observing can be done with no more than two or three well-chosen eyepieces. With eyepieces, you get what you pay for, so you'll be better off with two or three relatively expensive eyepieces than half a dozen cheap ones.
Filters are an accessory that appeal to beginners but get little use from experienced observers. Most of these filters are colored pieces of glass that screw into the bottom of eyepieces and are advertised to reveal all sorts of hidden details, primarily in planets.
In fact, these are specialized tools used by only a handful of advanced planetary observers, and are pretty much a waste of money for most skywatchers, unless you like to look at oddly colored planets.
The one filter that many astronomers use is a nebula filter, often mistakenly called a "light pollution filter." These filters pass the light only from the limited regions of the electromagnetic spectrum where nebulas glow. They do not make nebulas brighter; instead, they make everything except nebulas fainter. By dimming down the sky background, light pollution, and even the stars, they make nebulas stand out by contrast. The nebula will still be very faint; it's just that everything else will be fainter.
In general, the most useful filters are those advertised as "narrow-band" nebula filters. These pass two main wavelengths, hydrogen beta and oxygen III, which are what the majority of nebulas emit. Avoid "wide-band" filters, which are mainly for photography, and "line" filters, which are mainly for large telescopes.
Orion's UltraBlock is a good example of a "narrow-band" filter. It's important to know that these filters really only help with two classes of deep sky objects: planetary nebulas and emission nebulas. Nothing will make galaxies easier to see except a trip to a dark sky site.
How about a filter that doubles the time you can use your telescope?
That's what a solar filter does. It enables you to safely observe the surface of our local star in breathtaking detail. These are called "full aperture" filters because they fit over the front of your telescope. They are coated with a highly reflective metal film that reflects 99.9 percent of the sun's light and heat away before it even enters the telescope, allowing for safe observation of sunspots. The best of these filters are made with Baader Astrosolar film, which is optically superior to glass filters. Kendrick makes these filters in sizes to fit any telescope: http://www.kendrickastro.com/astro/solarfilters.html
A planisphere or star finder is a clever device that lets you view a chart of the stars on a rotating wheel through a window representing the horizon. You set the wheel for a specific date and time, and it shows you what the sky will look like. More than that, it gives you a good sense of how the stars move across the sky during the night, and how the sky changes during the course of the year. Here's a good one: Night Sky Star Wheel
Planetarium software is the 21st century equivalent of a planisphere. Not only does it show you how the stars appear on a given night and time, but it also shows you where the planets, asteroids and comets are, how the skies appeared thousands of years ago, and how they will appear thousands of years in the future.
Some programs will even let you travel through space and view the stars as they appear on other planets and even from other stars. With some, you can zoom out of the Milky Way and observe our neighboring galaxies in three dimensions. It will also print out star charts and allow you to control computerized telescopes. [Starry Night software]
Red LED flashlight
Even a tiny peek at your star chart with a white flashlight will ruin your dark adaptation. Astronomers prefer flashlights with adjustable red LEDs, such as these fine ones made by Rigel. They hang around your neck on a lanyard, lighting your footsteps in the dark and never get lost.
A comfortable observing seat will help you see better. In particular, it makes it easier to hold your eye steadily at the eyepiece. A good seat is comfortable, adjustable in height, and provides back support. There are many plans online to make one yourself, and there are many commercial designs. Some of these are repackagings of "drummer's thrones," which may be less expensive if purchased at a local music store.
A good star atlas is an essential tool for planning your stargazing expeditions and finding your way among the stars. The absolute best atlas for most of us is the Sky & Telescope Pocket Sky Atlas.
Astronomy club membership
Every amateur astronomer can enjoy the fellowship and support of a good astronomy club. There are now astronomy clubs in just about every town in the world, and a simple Internet search on "astronomy club" and the name of your town should give you some leads.
What not to buy
Barlow lenses: Many people make a Barlow lens one of their first purchases. These seem like a good idea, offering to double or triple the magnifications of all your eyepieces. In practice, these turn out not to be such a good idea.
Barlow lenses encourage overmagnification while also reducing the resolution of existing eyepieces. They also increase the danger of dropping some expensive glass while juggling stuff in the dark. If you ask any experienced amateur astronomer, you will find that they almost never use a Barlow lens. So I'd recommend taking the money you might spend on a Barlow and applying it toward a good quality short-focal-length eyepiece instead. That's something you'll use every night, rather than once or twice a year.
This article was provided to SPACE.com by Starry Night Education, the leader in space science curriculum solutions. Follow Starry Night on Twitter @StarryNightEdu.
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This story was originally written for SPACE.com and is reprinted with permission here. Copyright 2012 SPACE.com, a TechMediaNetwork company.