How to Use a Telescope
Amateur astronomy can be a fascinating and extremely rewarding hobby, allowing anyone with a telescope and a clear view of the night sky to explore the universe. It is also one of the few remaining fields of science in which amateurs can make significant discoveries. In recent years, amateurs have discovered new comets, distant supernovae, newly-forming stars, and asteroids impacting Jupiter.
Using a telescope for the first time can be a bit intimidating, but a bit of knowledge and preparation can make the experience far more productive.
Setting Up And Testing Your Telescope
While the types of telescopes vary, generally they all will have similar components - an optical tube, tripod, mount, finder scope, and one or more eyepieces. It is a good idea to practice setting up a new telescope during the day a few times before taking it out at night. This will avoid a lot of needless fumbling in the dark on the first night of observation.
Setting up a new telescope during the day will also allow the amateur to get better acquainted with the equipment - how to aim and focus the telescope, understanding the magnification of different eyepieces, and checking for proper alignment of the finder scope.
The finder scope is a small, low-power scope mounted to the side of the telescope employing cross hairs at the center of its field of view. This finder scope is used as a guide to aim the main telescope precisely at a distant object. In order to work effectively, the finder scope must be perfectly parallel to the main scope.
Aligning the finder scope is best accomplished during the day. The main telescope should be aimed at and centered on a distant, stationary object - a tree top, roof apex, or utility pole usually works well. Note: Do not aim the telescope at the Sun. Once this object is in view in the main scope, the finder scope can be checked. The object in focus in the main scope should be dead center in the cross hairs of the finder scope. If not, the finder scope can be adjusted using the alignment screws holding it in place.
Location, Location, and Location
One of the most critical components of any telescope setup isn't a part of the telescope at all. It is the location where you will do your observation. Ideally, this should be a dark, open space with a clear and unobstructed view of the sky.
Living in a rural area has some significant advantages for amateur astronomers, as urban stargazers will have to contend with light pollution obscuring many fainter celestial objects. Since driving a few dozen miles out to the country isn't a very convenient option for the amateur astronomer, sometimes a rooftop or shadowed area will provide enough darkness to allow some decent observation.
Stability of the observation site is also an important factor. Backyard decks are usually not a great location, as their construction will cause the telescope image to wobble with each footstep. Asphalt driveways can also cause image distortion when observing in the summer, as they can radiate heat for hours after sunset.
Aligning The Telescope Mount
Once the telescope is assembled, tested, and set up at a good location, the telescope's mount may need to be properly calibrated. This depends on the type of mount you are using.
There are two main types of telescope mount: altazimuth mounts and equatorial mounts. Altazimuth mounts are relatively simple mounts that allow the telescope to move freely up-and-down and side-to-side. These are good for brief observations, but observing any object for a long period of time will require constant readjusting of the telescope as the Earth's rotation slowly moves the object out of view. There are some digitally-controlled altazimuth mounts that can be programmed to automatically track objects in the night sky, but these are likely out of the price range and skill level of the beginning hobbyist.
Equatorial mounts were invented to alleviate this problem. While they are a bit more complicated to set up, they allow the astronomer to perfectly track a celestial body as it arcs across the sky. In order to work, these mounts must be aligned with the pole star.
In the northern hemisphere, this is a relatively easy task. The northern pole star Polaris is a bright, naked eye star on the handle of Ursa Minor, the Little Dipper. Once the axis of the equatorial mount is correctly aligned with this star, the telescope will be ready to track any celestial object in its journey across the sky
In the southern hemisphere, finding the pole star is a bit more difficult. The southern pole star is Sigma Octantis, a faint star just barely visible to the naked eye. Approximating this point can be accomplished using an imaginary line extending the long axis of the Southern Cross constellation and an imaginary line perpendicular to the stars Alpha and Beta Centauri. Where these imaginary lines intersect is a point very close to Sigma Octantis. Of course, in the modern technological era, an even easier method is to use one of the many helpful star finder apps available for smartphones and tablet computers.
Last Step: Explore the Cosmos
Once you have your telescope set up at your optimal location and your mount properly aligned, you are ready to explore the universe. You might start with some nearby planets such as Venus or Jupiter, or some bright stars such as Sirius or Vega. More challenging observations may be bright nebulae such as the Helix or Dumbbell nebulae.
It is important to keep in mind that you will not be seeing perfectly-focused, Hubble-quality images of nearby planets or distant objects. The Earth's atmosphere distorts anything viewed through a telescope, turning Jupiter's moons or Saturn's rings into a blurry mess. Part of an astronomer's skill is the patience to continue observing celestial objects, waiting for those fleeting moments of atmospheric clarity that will bring details of a planet into view. Technology can also be quite helpful here, and amateur astronomers have been able to produce some high-quality images by compositing the best frames from video filmed on digital cameras, webcams, and camera phones.
Since their invention in the 17th Century, telescopes have expanded our view of the horizon, allowing us to view everything from distant ships to the origins of the universe. As an amateur astronomer, you can also be a part of this long, proud tradition.
Sources and Further Information
- How To Use A Telescope
Now that you have your observing site, learned to set up, and established a time to practice astronomy… Let’s learn how to use your telescope!
- 10 Mobile Astronomy Apps for Stargazers
Whether you’re a stargazer who can only point out the Big Dipper and Little Dipper, or whether you much prefer calling it Ursa Major and Ursa Minor, the following 10 mobile apps can help you in your stargazing pursuits.
- Using a Telescope
Once you've obtained an astronomical telescope, what can you expect of it? Both less and more than many new owners realize.
- International Dark-Sky Association (IDA)
The mission of the International Dark-Sky Association (IDA) is to preserve and protect the nighttime environment and our heritage of dark skies through environmentally responsible outdoor lighting.
- Bad Astronomy | Discover Magazine
Phil Plait, the creator of Bad Astronomy, is an astronomer, lecturer, and author. After ten years working on Hubble Space Telescope and six more working on astronomy education, he struck out on his own as a writer.