Telescopes are used to view celestial bodies such as planets, stars, comets, and sometimes even galaxies. A telescope can provide you with hours of fun gazing at the stars. Once you know a few basics, you'll know what to look for and what kind of telescope is going to work best for you.
There are three basic types of telescopes for home use. Each us defined by the way they use their lenses to gather light.
Refractor telescopes gather light through a lense at the front of the telescope tube. Light enters through this lense and is then focused onto a mirror and reflected into the eyepiece. As the aperture, or the diameter of the lense that collects the light, increases so does the price. In refractor telescopes, the price goes up quite sharply with increased aperture. Refractors are best for viewing lunar and planetary observations. This type of telescope also tends to do better in light polluted areas than other types of telescopes.
Reflector telescopes use a mirror at the back of the telescope to gather light, which is then focused and reflected onto another mirror, and up to the eyepiece. This type of telescope can give you greater aperture at a smaller price than a refractor telescope. However, you will need to adjust the optical alignment if you use it often or if it gets bumped. Reflectors are good for deep-sky observing. They also perform better in darker, less light polluted skies.
Compound (catadioptric) telescopes have a combination of refractor and reflector elements in them. They are compact and lightweight in comparison with the other two telescope designs. There are several different compound telescope designs. Two of the most popular are the Schmidt -Cassegrains and Maksutove-Cassegrains. Both are similar and use a lense at the back of the telescope to focus light on a mirror at the front of the telescope. The differences lie in the shape of the lenses and mirrors. This is a popular type of telescope because it can be used for general sky observing and performs well in both dark conditions and light polluted skies.
These are the basic elements that will tell you the strengths and weaknesses of the telescope you are considering.
Aperture is the single most important feature of the telescope because it determines image clarity. Aperture is the diameter of the lense or mirror used to gather light in the telescope. This lense is often called the objective. In general, your telescope should have an aperture of at least 70mm (2.8in). The higher the aperture the more clear and detailed the image will be. Aperture is more important than magnification because high magnification can still leave you with a blurry image. Regardless of viewing conditions, a telescope with a higher aperture will give you a better image than a telescope with high magnification.
Your objectives focal length will determine the magnification or "power" of your telescope. The magnification is determined by dividing the focal length by the eyepiece length, which is found on the barrel of the telescope. Most telescopes come with at least two eyepieces that can be changed for greater magnification.
The mount, while not directly affecting what you see, can affect your ability to focus on objects and make a huge difference in your viewing experience. There are several different types of mounts.
Altitude-azimuth mounts, or simply alt-az mounts, are tripods that can move left and right as well as up and down. They usually come already attached to the telescope.
Some telescopes come with a mounting block that can be attached to a camera tripod. However, be aware that a standard camera tripod may not be sturdy enough for a telescope.
Dobsonian mounts are wooden and are a variation of an alt-az mount. They are commonly found with reflector telescopes.
Equatorial mounts are meant to track the movement of the stars by staying on a single axis. They are larger than alt-az mounts and you will need to be able to locate Polaris, the North Star, to properly align them.
Motorized mounts use a keypad to automatically direct the telescope towards the celestial body you want to see. These are used with "Go to" telescopes that have the ability to enter your date, time, and location. Once this information is entered, the telescope automatically aligns itself to view your chosen object.
Keep in mind the type of viewing that you want to do. There are quality telescopes in all brands and varieties but these are the three mass-market brands that consistently perform well.
Celestron offers a wide variety of high-quality telescopes. They have models that can be used for everyone from amateurs to professionals. The SkyProdigy 130 or NexStar 130SLT are good for a serious hobbyist while the Cosmos 90GT WiFi is easy to use for a beginner.
Orion has easy to use telescopes that consistently provide clear images. For the beginner, the Orion StarBlast 6 is easy to work and has good viewing. The ShortTube 80 is compact and works well if you travel or have limited space.
Meade, like the other two brands, offers a wide range of products but in general their products perform well.
Always read reviews for the model that you are considering as models may upgrade or be changed over time. Make sure the model you purchase will work for the type of viewing that you want to do.