Amateur astronomy is a rewarding hobby filled with awe and wonder. There is nothing quite like looking through a telescope and seeing a planet, nebula or galaxy for the first time with your own eyes. Making the decision to buy your first telescope can be exciting. But how do you choose a telescope? What is the best beginner telescope? There are several factors to consider and unfortunately, the number of telescope types, brands, sizes, and wide ranging prices can be overwhelming and confusing.
This telescope buying guide provides some basic information on telescopes, the advantages and disadvantages of different types of telescopes, and addresses what features to look for and details to consider when selecting your first telescope. Our goal is to help you make an informed decision that satisfies your needs and meets your expectations. Let’s get started!
Try Before You Buy
Nothing beats hands on experience with a telescope. It would be a good idea to visit an astronomy club in your area and take part in a public viewing or star party. Club members are typically happy to show you their telescopes and you’ll be able to test out several types and sizes. Some astronomy clubs even offer loaner or rental telescopes. It’s always better to try before you buy in case you realize that you weren’t really that interested in astronomy.
Find a local astronomy club by visiting one of the following links:
A good rule is to buy the biggest telescope you can afford. However, the best telescope is the one you’re going to use most often so you need to consider portability.
If you only intend to use it in your backyard then a large telescope may not be an issue. If you need to drive away from the city to avoid light pollution, you’ll need to make sure the telescope can fit easily in your vehicle. You should also think about how comfortable you’ll be lugging around a large and heavy telescope. For example, an 8″ Dobsonian mounted reflector can weigh around 40lbs and measure almost 4 feet long.
Start With Binoculars
One of the best ways to introduce yourself to amateur astronomy is with binoculars – you might already own a pair. If your telescope budget is $100 or less, astro binoculars are the best option. With an extremely wide field of view, binoculars are a great way to learn how to navigate the night sky and the constellations especially if paired with a good astronomy book for beginners.
With binoculars and good viewing conditions, you will be pleasantly surprised at the number of night sky objects you can see. Expect to see more stars than with the naked eye, comets, planets, star clusters, nebulae and galaxies. The craters of the moon will also be visible as well as the moons of Jupiter. However, you will not be able to see any details of the planets and a telescope will reveal much greater detail of the moon.
For stargazing, the most popular astro binoculars are 10×50. The first number represents the magnification (10 times) while the second number is the diameter of the main lens measured in millimetres (50mm) also known as the aperture size. A higher magnification will allow you to see fainter objects and finer details but will reduce your field of view. It will also magnify the shakiness when holding your binoculars by hand. Resting your elbows on a solid surface like a table or using a tripod will minimize shaking especially if the magnification is greater than 10x.
Binoculars are the perfect companion to a telescope and they should last a lifetime. Being lightweight and extremely portable, binoculars are great for quickly and easily locating celestial objects in the sky.
What can you expect to see through a telescope?
This will depend on many factors including the type and size of telescope, skill-level, light pollution and local seeing (atmospheric) conditions.
With a constantly changing face, the moon offers excellent details even with a small telescope including craters and mountains.
- Jupiter provides the most detail of the planets offering views of its cloud bands, Great Red Spot, and 4 Galilean moons
- Saturn’s rings and its largest moon, Titan
- Mars and its polar ice caps (best every 2 years when closer to Earth)
- the changing phases of Mercury and Venus
- Neptune and Uranus will appear star-like
The sun offers plenty of detail including multiple sunspots and surface granulation. You must use a proper solar filter when viewing the sun through a telescope. Failure to do so can result in severe eye damage.
Due to the extreme distance between the Earth and the stars, stars will only appear brighter through a telescope and not larger. You will observe many stars as pairs through your telescope. These binary stars or double stars consist of two stars, usually of different colors, orbiting around their common center of mass.
Aperture, Focal Length, and Magnification
The most important specification to look for when choosing a telescope is aperture. Aperture is the diameter of the telescope’s light-gathering lens or mirror (also called the objective). The larger the aperture, the more light will be collected resulting in brighter and sharper images. Aperture is typically measured in millimetres or inches. Doubling the aperture increases the surface area by a factor of four. For example, an 8″ diameter lens or mirror will collect four times as much light as a 4″ diameter lens or mirror.
A telescope’s focal length is the distance from the objective lens or mirror to the focal point. Longer focal lengths result in higher magnification, larger images and smaller fields of view.
The focal ratio (f/ratio) is equal to the focal length of the telescope divided by its aperture size. For example an 8″ (203mm) aperture telescope with a 1200mm focal length would have an f/ratio of f/5.9 (1200 divided by 203 equals 5.9). Smaller f/ratios result in lower magnification and wide fields of view. Higher f/ratios result in higher magnification and narrow fields of view.
Perhaps the biggest misconception is that a telescope with high magnification (also called power) is required to see celestial objects. Magnification is one of the least important factors to consider. You can change the magnification of your telescope by switching eyepieces with different focal lengths.
Magnification is calculated by dividing the focal length of the telescope by the focal length of the eyepiece. For example, a telescope with a focal length of 1200mm and an eyepiece with a focal length of 25mm would provide a magnification of 48x (1200 divided by 25 equals 48).
As a rule of thumb, the maximum useful magnification for any telescope is 50 times the aperture in inches or two times the aperture in millimetres. For example, a 6” (150mm) reflector would have a maximum useful power of 300x. At higher powers, atmospheric conditions will distort and blur the image seen through a telescope. Therefore, the practical upper limit of magnification for any telescope is considered to be around 300x even if the theoretical upper limit is calculated to be higher. Most telescope viewing is done at low power anyways.
Different Types of Telescopes
There are three main types of telescopes:
This is the image most people have when thinking of the word “telescope”. The first telescopes were refractors. A refractor telescope has a convex objective lens at the front end of a sealed tube and an eyepiece at the rear end. There are two basic types of refractors: achromatic and apochromatic.
Refractors are easy to use, reliable, require little to no maintenance or adjustment, and accumulate very little dust. They are excellent for lunar, planetary, and binary star observing, however the smaller apertures make it difficult to view dim deep-sky objects.
Refractors have the highest cost per inch of aperture. Larger aperture refractors can be very long and heavy compared to equivalent aperture reflectors or catadioptrics. They require a tall and bulky mount as the eyepiece is located at the rear.
Apochromatic refractor telescopes are quite expensive due to need for additional lenses made from special types of glass to correct an effect known as chromatic aberration. When light passes through the objective lens, each wavelength of light is refracted by a different amount and the colors fail to converge at the same focal point. Think of the rainbow effect of light passing through a glass prism. Chromatic aberration is typically seen as color fringing around bright objects, like a purple halo around planets and stars.
One added bonus with refractors is that they can also double as a terrestrial telescope for daytime distance viewing of landscapes, landmarks, boats or wildlife.
- easy to use
- little to no maintenance or dust with sealed tube
- excellent for observing moon & planets
- can use for daytime terrestrial viewing
- highest cost per inch of aperture
- difficulty viewing dim deep-sky objects
- larger apertures are long & heavy
- chromatic aberration
- require tall & bulky mount
- uncomfortable viewing angle
Reflector telescopes, also known as Newtonian telescopes, are not sealed tubes like refractors but are open at one end. Instead of an objective lens, a concave primary mirror collects and focuses incoming light onto a flat diagonal secondary mirror which reflects the image to an eyepiece on the side of the tube.
They offer the best value per inch of aperture of the three types of telescopes due to the cheaper manufacturing costs for mirrors than for lenses. This relatively low cost results in much more affordable large apertures which are perfect for viewing deep-sky objects.
A Dobsonian telescope is a large aperture Newtonian reflector on a simplified altazimuth mount that sits on the ground. Dobsonians are very popular with beginners. They are easy to setup, simple to operate and offer the best bang for your buck.
Occasional cleaning may be required as the open tube allows dust, pollen, and dirt to accumulate on the mirrors. The mirrors can also get out of alignment and require periodic manual adjustment called collimation. Collimation is not a time-consuming or difficult process although it may take some practice. Instructions should be included with your telescope.
Reflectors do not suffer from chromatic aberration but they do have a different type of optical aberration known as coma. Coma gives stars a wedge-shaped appearance near the edge of the field of view, however stars in the center of the field of view are unaffected. Coma is more noticeable in reflectors with smaller f/ratios.
- best value – cheapest per inch of aperture
- perfect for viewing deep-sky objects
- large apertures – light-buckets
- no chromatic aberration
- Dobsonians are extremely easy to use
- comfortable viewing angle
- mirrors collect dust, pollen, dirt with open tube
- requires occasional collimation
- Dobsonians are large and heavy – portability & storage issues
- not good for astrophotography
Catadioptric (or compound) telescopes use a hybrid design with a combination of lenses and mirrors in a sealed tube which fold the optical path to form an image. This provides a focal length much longer than the length of the compact optical tube. They are more commonly known by the two popular designs: Schmidt-Cassegrain and Maksutov-Cassegrain.
Catadioptric telescopes offer the most compact and lightweight design resulting in high portability and easy mounting. Cost per inch of aperture is midway between reflectors and refractors.
They are the most versatile of the three telescope types with great viewing of the moon, planets, and deep-sky objects, as well as the ability for daytime terrestrial viewing and astrophotography. They are very easy to use.
The optical elements of Maksutov-Cassegrain telescopes are typically fixed in alignment and do not require collimation. Schmidt-Cassegrain telescopes may require occasional collimation but it is a much easier process than collimating a reflector telescope. The sealed design eliminates dust and dirt, and little if any maintenance is required. Catadioptrics have the longest cooldown time (thermal stabilization) of any design which means you’ll have to wait longer for optimal viewing.
- compact & lightweight – best portability
- easy mounting
- easy to use
- good for viewing planets & deep-sky objects
- daytime terrestrial viewing
- excellent for astrophotography
- more expensive than reflectors
- occasional collimation for Schmidt-Cassegrain
- longest cooldown time
- narrowest field of view
The optical tube is only one half of a telescope – the other half being the mount. It is just as important as the optical tube. The mount keeps the telescope steady by minimizing shaking. Vibrations are magnified at high power and a shaky view will render even the best telescope useless. As the Earth rotates, celestial objects will appear to move across the sky. The telescope will need to be frequently moved in small increments to keep on object centered in view. The mount should allow these movements to be done as smoothly as possible.
The two types of telescope mounts are altazimuth and equatorial.
Altazimuth (alt-az) mounts are the most common type of telescope mount. They move up and down (altitude), and side to side (azimuth) similar to a camera tripod. Tracking celestial objects across the sky is done by moving the telescope with your hand or by using slow motion controls, depending on the model. The drawback to an altazimuth mount is that it requires simultaneously adjusting both axes.
Dobsonians are an extremely popular type of altazimuth mount for large reflector telescopes due to their simplicity, ease of use, and low cost. A good way to picture a Dobsonian is a see-saw on a lazy susan.
Equatorial (EQ) mounts are more precise than altazimuth mounts. Aligning one axis with Polaris (the North Star) will allow you to adjust only the polar axis to track an object as the Earth rotates. There is a learning curve to understand how to operate an EQ mount but once you’ve figured it out, tracking celestial objects becomes much easier as you only adjust a single knob.
Many equatorial mounts are heavier than altazimuths because they require a counterweight to balance the telescope. An equatorial mount is the best option for astrophotography.
Computerized or GoTo mounts are becoming increasingly popular. They come with a small motor drive, built-in computer and hand-held controller which allows you to look up celestial objects in a database. The GoTo will automatically locate the specific object and track its movement across the sky. All you have to do is look through the eyepiece.
If you want to learn how to navigate the night sky, go with a manual mount. GoTo mounts remove the required practice and skill for locating celestial objects. There is also a trade-off with optical quality as the electronics typically eat a few hundred dollars of your budget, leaving you with a smaller aperture. For the same price as a GoTo model, you could purchase a non-computerized telescope with a much larger aperture and better viewing capabilities.
This guide focuses on the basics of buying a telescope. Astrophotography can be quite complicated and expensive, and we suggest beginners first learn the basics of operating a telescope before diving into astrophotography. Although astrophotography can require specialized equipment and accessories, most telescopes can be combined with a camera.
As mentioned above, if your budget is $100 or less, serious consideration should be given to purchasing binoculars instead of a telescope. There really aren’t any telescopes worth buying in this price range. Telescopes are precision optical instruments and the lenses and mirrors can’t be manufactured cheaply without cutting corners. A cheap telescope is essentially a toy and you’ll quickly be disappointed and left wondering why you wasted your money.
There aren’t many good options for under $200 either. Another reason sub-$200 telescopes are not recommended is due to the low quality mounts which are simply not stable enough to be usable. Many of the mounts included with telescopes in this price are actually camera tripods. There certainly are a few exceptions including some tabletop telescopes. If you can wait, it might be best to save a little bit more money for a better quality telescope.
Serious beginners should plan for a budget of $300 to $400. This would allow you to buy a 6” Dobsonian mounted reflector telescope, a starter book on astronomy, and an extra eyepiece. This budget would allow you to purchase an 8″ Dobsonian, however there wouldn’t be any money left over for a book or accessories. There are other options with smaller apertures in this price range including refractors, non-Dobsonian reflectors and Maksutov-Cassegrain telescopes but you’ll get the best value with a Dobsonian.
If your budget is higher than $400, there will be plenty of quality options available including larger aperture Dobsonians and GoTo mount catadioptrics. Expect to spend a minimum of $700 for a decent GoTo telescope with a 5″ aperture. There are cheaper GoTo alternatives, however the apertures will be smaller and the optics will be of lesser quality.
- try to get hands-on experience with a telescope before you buy
- consider size, weight, and portability
- start with binoculars
- aperture is the most important factor to look for when buying a telescope
- ignore magnification – can change by switching eyepieces
- learn the basics before trying GoTo Mounts or astrophotography
- Dobsonian reflectors offer best value
Low Budget Telescope
If there are any astronomy words or terms that you’re still unclear about, check out our Glossary of Astronomy Terms.