A variety of tools can enhance your stargazing by helping you locate objects in the sky and see them in more detail.
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Star charts are road maps for the sky: they show the locations of stars, galaxies, nebulae, and clusters, as well as directions (north, south, east, west) and degrees to help you find them. A good starting point is a planisphere, a circular map that lets you adjust the view depending on the season. There are different planispheres for different latitudes, so make sure to get one that matches your location.
How to Use a Star Chart
Star charts never look exactly like the night sky and can be confusing at first. To get used to using them, try these tips:
- Remember that star charts are meant to be held upside down, so unlike regular maps, west will be on the right, and east will be on the left.
- Hold the chart so that north on the chart faces the north horizon (see How to Get Oriented in the Night Sky).
- Bigger dots on a star chart represent the stars that are brightest (and easiest to spot), so try finding these first.
- Don’t use a regular flashlight to view your star chart, because that will make it hard for your eyes to readjust to the dark. Cover your flashlight with a red filter (such as red cellophane) or use a dim flashlight specifically designed for stargazing purposes.
- Note that objects not on the celestial sphere—planets, comets, asteroids, and satellites—don’t always appear on star charts. (To find them, see “Planet-Finding Charts” and “Ephemerides,” later in this section.)
- Don’t expect every star on your chart to be visible if you’re observing an urban sky (or if it’s near Full Moon), and don’t expect every star in the sky to be on your chart if you’re observing a very dark sky.
Star charts indicate how bright objects in the sky are, using a magnitude system. The lower an object’s magnitude, the brighter the object is, and the easier it is to find. A decrease of 5 magnitudes means a 100x increase in brightness.
Most stars and galaxies have positive magnitudes, whereas brighter objects such as planets and the Moon have negative magnitudes. The following chart lists a few objects of various magnitudes, from brightest to dimmest.
Venus (the brightest planet)
Sirius (the brightest star)
Vega (a prominent star in the Summer Triangle, around which the magnitude system is based)
Limit of what you can see with the naked eye in urban locations
Limit of what you can see with the naked eye in dark locations
Limit of what you can see with binoculars in dark locations
Limit of what the world’s largest telescopes have observed
Most planispheres show only objects that are brighter than magnitude 4.5, whereas larger star charts show objects brighter than magnitude 6 or so.
Planets don’t move with rest of the sky but instead follow the path of an invisible line called the ecliptic. As a result, you can’t depend on landmarks such as the North Star or constellations to locate them. In a given evening, a planet might be visible for all of the night or part of the night, or it might not be visible at all. Each planet is visible within a fixed schedule that may not change much over a few days but will be drastically different after a few weeks.
Planet-finding charts, found in astronomy magazines or online (see Stargazing Resources), give you a rough idea of where to find planets at different times of year. They usually will point you to the constellation nearest to the planet.
Ephemerides (singular ephemeris) are tools professional astronomers use to locate the exact positions of planets, asteroids, comets, the Moon, and other satellites. They are tables or data files containing the celestial coordinates of an object at regular intervals throughout the night. You can generate ephemerides easily online (see Stargazing Resources).
Binoculars are an inexpensive, lightweight alternative to telescopes. With a good pair, you can spot objects as faint as magnitude 10. The most popular types of binoculars used for stargazing are:
- 7×50: magnifies 7 times and has a 50mm aperture (front lens size)
- 8×35: magnifies 8 times and has a 35mm aperture
The 8×35 magnifies more powerfully but collects less light than the 7×50, so the 8×35 is not as good for observing very faint objects. High-end binoculars (so-called supergiant binoculars) range up to 20×100 or above and look more like twin telescopes than standard binoculars.
Your hands will shake when holding any type of binoculars, making fainter objects difficult to see. It’s best to prop your binoculars up on something steady, or get a binocular holder or a tripod.
Telescopes are essentially buckets for collecting light— the bigger the telescope, the more light it will collect, and the better you’ll be able to see faint, distant objects. Telescopes can be pricey, though, so before you buy one, put careful thought into which type is best for you. There are three main categories of telescopes: refractors, reflectors, and catadioptrics.
(uses lenses only)
(uses mirrors only)
(uses lenses and mirrors)
There are countless telescope accessories you can buy to aid your stargazing ventures. Some are absolutely necessary, and others are essential only for professionals.
- Mount: An essential accessory, a mount holds the telescope steady and lets you aim it at different points in the sky. There are two types of mounts: azimuth, which allows you to move the telescope up and down and in lines parallel to the horizon, and equatorial, which is aligned with the celestial poles. Azimuth mounts are best for beginners.
- Eyepiece: An eyepiece, which determines your field of view, is also essential for telescope stargazing. Most telescopes come with an eyepiece, but rarely a good one. Eyepieces are categorized by focal length (in mm) and barrel size (1.25″ is standard). Larger focal lengths mean wider fields of view, and larger barrel sizes make better eyepieces.
- Filter: Though not absolutely essential, a filter reduces glare, increases contrast, protects your eyes, and increases the definition of what you see through the telescope. The most popular filters are lunar filters, planetary filters, and solar filters. You should never observe the Sun without using a proper solar filter.
- Drive system: A drive system makes the telescope track the sky and keeps objects from drifting out of your field of view. It isn’t essential, but you’ll need one if you plan to use your telescope for astrophotography. This requires you to align the telescope to the Earth’s polar axis, however, which can be time-consuming.
- Computer-driven mount: This type of mount allows you to tell the telescope what you want to observe, and the computer then finds it for you. Many expensive telescopes come with a computer-driven mount, which makes it quick and easy to find faint objects in the sky and may even let you control the telescope from a laptop. The flip side, though, is that a computer- driven mount takes some of the fun and challenge out of stargazing.
- Dew shield: An optional accessory, a dew shield is a long tube that slips over the front of the telescope to slow the condensation of harmful moisture (dew) on the telescope, which often happens on damp nights.
- Barlow lens: A Barlow lens is another optional accessory that connects to the eyepiece and can bump up magnification by 2x or more. It’s important that the Barlow lens be the same barrel size as your telescope’s eyepiece. Also note that any objects you view become dimmer the more they’re magnified.
Tips for Using Telescopes
Telescopes can be tricky to use, and it takes a lot of practice to become completely comfortable with them. You’ll be at an advantage, though, if you remember a few tips:
- Know that refractor and catadioptric telescopes make objects appear upside-down. Most objects you’ll be viewing will be roughly symmetrical, so this won’t seem obvious at first. It might disorient you, though, when you start to move the telescope, and it can make using a Moon map a bit confusing.
- Know that reflector telescopes make objects look backward. This can also be disorienting, especially after you’ve been looking through other types of telescopes.
- Practice star hopping. Point your telescope on a star you recognize, and with the help of a star chart, identify a trail of stars that lead to the faint object. You can then “hop” from star to star along this trail with your telescope—the smaller the hops, the better—and end up at the object you were searching for.
- Don’t forget that the Earth is constantly rotating—which means that objects in the sky appear to move (see How to Get Oriented in the Night Sky) and will drift out of your telescope’s field of view, often faster than you’d expect. If you don’t have a drive system, you’ll need to nudge your telescope every few minutes to follow an object.
- Use averted vision: when trying to view very faint objects, look a bit to the side of where the object is, and you’ll actually see it better. The edges of your retina are better at detecting faint objects than the center, which is more sensitive to color than to brightness.
- Never use a dirty cloth to clean your telescope. Telescope lenses and mirrors can easily be scratched or damaged, so use chamois leather or a clean, soft cotton handkerchief. And be careful with glass-cleaning cloths—some types of cloths can actually rub off the special coatings from telescope mirrors.
- If you wear eyeglasses, take them off. You’ll see better if you put your eye right up to the eyepiece, and you can simply adjust the telescope’s focus knob to compensate for your vision.