Tips for Buying a Telescope: the Future is Here, and it’s Awesome
Way back at the dawn of the 21st Century, astronomy could be difficult, confusing, time consuming, and often, simply frustrating. But now, the future is here, and astronomy has taken on an entirely new dimension. We’re going to look at the current state of astronomical instruments, and show that there truly is a telescope for anyone at every experience level.
The most common formula for people purchasing a telescope is to balance these three factors:
The difficulty with this approach is that there are several key components missing:
Let’s take a look at what these six equally important pieces are and why they are critical to choosing the right telescope.
The quality of the telescope determines how well you will see your subjects. It's determined by the type of glass from which the lenses are made, the type and grade of anti-reflection coatings on the lenses, and reflective coatings on mirrors and prisms, as well as the composition of the optical pathways. A high-quality 90mm telescope will probably provide better views than a lower-quality 120mm scope will.
Usability isn't only about the capability of the optical system in a telescope, it also concerns the objective diameter (bigger is always better) and focal length (longer is usually better). Usability is also influenced by the mount and tripod.
The "objective" is the main light-gathering optic. On a refractor, it’s the front lens. On a reflector, it’s the primary mirror. The objective size determines how much light is brought into the optical system, so the bigger the objective, the more light it’s bringing to your eye, so with larger objectives, you’ll be able to see dimmer subjects more easily, which tend to be further away.
The focal length is the distance needed by the objective to bring all of the light collected to one point (the focal point). In traditional telescopes like refractors and reflectors, this is a linear measurement; however, on more advanced telescopes, such as a compound telescope, the focal length becomes a mathematical distance determined by a series of lenses and mirrors, and will be much longer than the actual size of the OTA (optical tube assembly). Your focal length directly determines the magnification potential of the telescope, and longer is better.
A telescope mount called "alt-azimuth" provides basic point-and-look ability, but it's really only good for the biggest and brightest objects: the Moon, planets, and some stars; and it may or may not have the ability to track.
A "German equatorial" mount requires more setup and knowledge, but you’ll be able to find just about anything overhead and track it throughout the night—the only limitations are those imposed by your telescope’s ability to see them. A "manual EQ" mount will require it to be aligned with the pole star. In the Northern Hemisphere this is Polaris, in the Southern there really isn’t one as good as Polaris, but these days most people use Sigma Octantis. A manual EQ mount will have control cables to track subjects, and some will come with motors to automatically track after you’ve found what you’re looking for. This type of mount requires a lot of prep work before going out to observe, and a high degree of patience to set up, align, and find your subject.
Computerized mounts are becoming more common as their prices drop. Most computerized mounts will also be motorized, with the computer guiding the speed and direction of the motors. The computerized telescopes we’ll be discussing in this piece not only guide, but help the user to set up and align the scope with full “go-to” capabilities. This ability to go to any point in the night sky eliminates the need for a lot of research beforehand, and you can leave the star charts at home because the onboard computer has all that info built in.
This factor may be the trickiest of all. As I discussed in my article about why astronomy is becoming popular these days (inspiringly named “5 Reasons Why Astronomy is Popular”), there has always been a catch-22 with purchasing a telescope as a present—especially for children or young adults: You’re reluctant to spend too much in case astronomy is just a passing phase, but unless you spend some money, you can’t get a scope that's capable of inspiring the user to get into it more. And therein lies the dilemma. Luckily, we’re living in the future, and motorized/computerized telescope prices have been steadily falling as technology has been advancing. They provide real options without necessarily breaking the bank.
|The common perception of Saturn||What Saturn looks like through a telescope|
This factor deals with the gap between what you expect to see through a telescope and what you’ll actually be able to see. Most young people in their 20s or younger haven’t lived in a world without the Hubble Telescope, nor can they remember a time when they couldn’t immediately check out pictures on the Internet. This generation has literally grown up on high-resolution images of space and Mars, and the general Universe. As a result, they probably expect Saturn and its rings to look like what they saw when they Googled it. It won’t. It’s going to be small—really small. It’s going to look like Saturn, but just a smaller version of it, compared to what they saw on their iPad. But here’s the thing: they’re going to see it live. Young people need to be aware of this before you invest in a telescope. Take a spin around the Internet with them and make sure their interest survives. No matter how much money you pour into buying a telescope, there’s very little chance that anything you look through will compare to images that are taken in space and professionally manipulated.
Similar to Usability above, Ability is a function of the person using the scope. A young person may lack the fine motor skills or basic understanding required to operate an EQ mount, or maybe even to accurately track an object manually. They also will have a harder time conceptualizing the notion of a galaxy, nebula, or binary star system. For children, stick with a basic scope for viewing the Moon and planets. Many children (and a fair number of adults—this one among them) are fascinated by making detailed observations of the Moon. Basic planetary viewing is both rewarding and fairly easy. Since the Moon and planets are easy to spot with the naked eye, they’re easy to find with a telescope. An EQ mount allows you to get a much larger aperture, or higher-quality scope (or maybe both) for the same price as a smaller computerized/motorized one.
What is the user interested in viewing: near space or deep sky? It may sound obvious, but it needs to be said: different people have different interests. While bigger is usually better, if someone is looking to observe the Moon, you may want to invest in a higher-quality optical tube. If someone is only interested in deep sky objects like nebulae, then a bigger scope like a Dobsonian might be more appropriate, as long as the recipient has room for it.
|Moon, near-space||Nebula, deep sky|
Types of Telescopes
Now that we've covered the basics, it's time to look at the types of telescopes available. There are three basic designs:
- Compound (or Catadioptric)
This is what most people picture when they think of a telescope. There's a lens at the front and an eyepiece at the back. This was the first type of telescope Galileo used when he made his initial observations of the Solar System. Because of the extra work involved in grinding and assembling the lens systems, they tend to be more expensive than Reflectors. The advantage to the Refractor is that by using a combination of lenses and lens coatings, designers are able to achieve very clear and crisp images without distortion or "halos" around objects like stars. Refractors tend to be a bit of a trade-off. Smaller apertures mean you won't see as deeply into space, but the objects you will see generally are clearer and cleaner. If the person is interested in astrophotography or astro-imaging, this type of telescope is generally preferred for this reason.
These telescopes use mirrors where refractors use lenses to get the light to your eye. A typical configuration has the front of the long optical tube assembly (OTA) open, with a mirror at the back. A smaller, secondary mirror is located about 2/3 of the way toward the front of the OTA. This mirror directs the light into the eyepiece, which is located on the side of the scope. These scopes are often considered to be more comfortable for viewing, since most people can stand up and reach the eyepiece. Mirrors are less expensive, and assembling reflectors is generally easier, so you will often find larger aperture reflectors for the same or less money than smaller refractors. The downside to reflectors is that the optical path is less precise, so images might not be as pin-sharp. The upside is that you’ll be able to see more. In a practical application, if you have little or no experience looking through a telescope, chances are you won’t notice that the images are not as sharp as they could be.
A sub-set of reflectors called "Dobsonians" needs to be mentioned. These are very large telescopes that are typically more than 10" in diameter and can stand more than 6' tall. They are most often used by experienced amateur astronomers who have taken smaller scopes to their absolute limits. Dobsonians take up a lot of room and are difficult and bulky to move, but they offer views that most of us will never see. They can be used for astrophotography and astro-imaging to get awesome shots of distant celestial objects, such as nebulae and galaxies.
This type is also called a compound or Cassegrain telescope. They use a combination of lenses and mirrors to produce their images, and have focal lengths much longer than their compact optical tubes. The advantage of this type of telescope is that it's capable of producing high magnifications with excellent image quality in a compact package. It's easier to store and takes up less space for transporting.
As we discussed above, deep-space objects often take beginners too long to find. The Moon and planets are easy to find, and are easy to conceptualize and understand. Deep-space objects like nebulae or star clusters probably won’t make the same impact as closer objects. The rings of Saturn or the craters of the Moon are awe-inspiring sights, and easy to see. The Celestron Travel Scope 70mm Refractor is a basic and capable telescope that comes with a custom backpack for easier transportation away from civilization to make your observations. The Meade 90mm StarNavigator Refractor is light and easy to set up, with a motorized mount and computer controller. This controller, the AutoStar, offers Go-To features with virtual guided tours and audio explanations of what you're viewing. Another excellent choice for beginners is the larger version of the StarNavigator. With the larger aperture, you can see beyond our solar system. These two telescopes offer fast setup, and the Go-To capabilities draw inquisitive eyes skyward and away from their smartphones.
For intermediate-level people or those with a proven interest in astronomy, you have some excellent choices that include manual and motorized options. Celestron’s AstroMaster 114EQ Reflector gives your purist or mechanically inclined person the challenge of learning a traditional equatorial mount and the thrill of relying solely on themselves and their ability to find the objects they want. I can tell you from experience—spending days learning to use the mount, researching what I want to see, then finally taking the scope outside and spending some time aligning and manipulating the scope—when you finally look through the eyepiece and see exactly what you were looking for, it's something that will stay with you for years, if not the rest of your life. Also from Celestron is the future of astronomy: the COSMOS 90GT 90mm Refractor with Wi-Fi. This has a built-in Wi-Fi transmitter that connects to Android and iOS mobile devices running a free app. When connected, the phone or tablet becomes the controller, and the app has expanded descriptions, videos, guided tours, and more ever-increasing capabilities. For a more compact unit, look at the Celestron NexStar 127SLT. It has the NexStar computer hand-controller that works in a similar way to the AutoStar from Meade. Since it’s a catadioptric design, it’s powerful and portable while still offering computer control and motorized tracking.
Upping the capabilities is Celestron NexStar 6SE and its 8" sibling. Similar to the 127SLT, these have much larger apertures, so they’re more geared to deep sky viewing and astro-imaging. For a more experienced user who’s looking for deeper sky, there’s the Sky-Watcher 10" or the larger 12" Dobsonians. Again, before you jump into these, make sure the person you’re giving it to has the room to store them—they're the opposite of compact.
For the very experienced observer who is looking for either an imaging scope or just a portable OTA for quick sessions, Tele Vue offers an 85mm Apochromatic or NP-101 Apochromatic refractors that have incredible capabilities and are ideal for imaging. The 85mm is offered without a mount or tripod, and the NP-101 without a tripod, so make sure the user has those things before investing in either of these precision instruments.
An emerging area of interest for photographers is wide-field astrophotography. iOptron’s SkyTracker Camera Mount is specifically designed to accept DSLRs and will compensate for the Earth’s rotation to allow for long exposures. These long exposures produce incredibly detailed shots of the sky without star streaks.
In a category all by itself is Celestron’s SkyQ Link 2 Wi-Fi Module. It simply plugs into the mount of most Celestron computerized telescopes and replaces the NexStar controller. It emits its own Wi-Fi signal to connect to smartphones and tablets to expand the user’s experience with enhanced alignment tools, guided tours, and it offers videos for select objects that explain the history, mythology, and key features of the most popular celestial objects. If you’re giving a gift to a person with a computerized Celestron telescope, this is something they must have.
There is no doubt that telescopes make excellent gifts for people of any age, interest, and experience. Even if the person you’re buying for already has their favorite telescope, there are many accessories to expand their use and capabilities.
Technological advancements have made astrophotography and astro-imaging accessible to more people than ever before. Camera adapters, CCD eyepiece cameras, software, and computer interfaces make capturing and editing your own photos and movies easier than ever.
Eyepieces and filters are always appreciated and they're often interchangeable, since there are industry-standard sizes like 1.25" or 2", and the less popular 0.965". Finderscopes and alignment tools are also underappreciated and overlooked gift options that even the most experienced observer can enjoy.
If you have any questions about telescopes and their accessories, we encourage you to ask them in the Comments section, below.