Human beings have been stargazing since the beginning of time. Our fascination with the cosmos is a connection to our origins. And the more we learn about our universe, the more fascinated we become, and the more excitement astronomy holds. But if you want to get a good look at the stars, you first need a great telescope. Buying a telescope can be a daunting task, especially given the myriad choices a quick internet search will lay at your fingertips. Do you need a refractor or reflector? What kind of magnification and lenses? What’s the best telescope for the activities you love? We’ve devised this guide to help you choose the perfect telescope without stress, so you can focus on the cosmos instead.
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The first conundrum you’ll likely face in your search for the perfect telescope is which style you need. Economy plays a role here, but so does the lifespan you want from your telescope, the size that works best for your space, and the magnification power you need.
A refractor is built with convex lenses. The objective (main) lens pulls in light waves, and when they reach their focal point inside the telescope tube, the eyepiece lens absorbs them. Refractors are the least expensive type of telescope, are usually lightweight, and most come with a changeable eyepiece lens to vary your magnification strength. Refractor scopes are great for beginners, and perfect for checking out the moon or planets in our solar system. They won’t have enough power, however, to get a good look at deep sky objects.
Instead of an objective lens, reflector telescopes are built with mirrors to bounce light through your telescope tube, elongating the focal path to give you more magnification power with a smaller tube. These are great for deep sky viewing of subjects like galaxies and Messier objects. But reflector telescopes are larger and heavier than refractors, and more expensive. They also require a bit more maintenance to keep them in top shape.
A common name for a catadioptric telescope is Schmidt-Cassegrain, or SCT, after its inventors. An SCT folds light inside the telescope tube using a combination of lenses and mirrors. This makes the focal path even longer and the magnification stronger than a refractor or reflector. Many SCT telescopes are computerized, as well, which gives you some great added options for astrophotography. While they do require almost no maintenance, SCT telescopes are also much more expensive.
In a telescope, the magnification power is determined by the eyepiece and the focal length of your telescope tube, both of which are usually printed on your telescope. You can find the magnification power of the telescope by dividing the focal length by the size of the eyepiece. If you have a 900mm focal length and a 90mm eyepiece, then you have 900/90 = 10x magnification. If you want more magnification strength, a longer focal length (determined by the length of the light path) and a smaller eyepiece will get you there. Higher magnification doesn’t always mean a better telescope, though. If you want sharper images, you want less magnification. Higher magnification will deliver better distance, but the images will tend toward the blurry side.
This is where you can bring your telescope’s quality to the next level. Here are a few options to enhance your telescope’s capabilities.
This is a concave lens that sits between the objective lens and the eyepiece to increase magnification power. If you purchase a 2x Barlow lens, for instance, and you have a 50x magnification strength on your telescope, the Barlow will boost it to 100x magnification. They’re easy to attach to your eyepiece, but make sure you know the width of your eyepiece barrel first, so you buy the right size.
Depending on the type of telescope you buy, you may need to consider image distortions such as chromatic or coma aberrations. These are caused when different colors are filtered at different speeds through your lens, causing halo or blurring effects around the image. You can purchase an achromatic or apochromatic lens to get rid of chromatic color distortion, or a coma correction lens for those fuzzy image trails. Another option is stopping down your lens, which means decreasing the aperture size.
You can get creative with lens filters. They block out unwanted light, and they can enhance the quality of astrophotography. Line emission filters will narrow your light absorption to a single wavelength to enhance nebulae viewing. Light pollution filters will cut out artificial environmental light to give you image clarity. Narrowband filters will decrease the number of wavelengths for added image contrast. You may want to buy a kit with a variety of filters to see what works best for your viewing.
Below are some common uses for your telescope, and what type of telescope or lens is best suited for each. Consider how you’ll be using your telescope, then read on to learn which one will work best for you.
Remember that lenses absorb light, so the bigger the lens, the more light will enter. The moon is a bright object, so aim for a smaller eyepiece to avoid eyestrain and give yourself the clearest image. A 10-20mm eyepiece is ideal, and around 60x magnification.
Our solar system’s planets are bright objects, as well, so try to avoid a telescope that gathers too much light. You’ll want a scope with a long focal length and a little more magnification. While SCT telescopes are more expensive, they’ll give you that long focal length and the best planet-viewing capacity. A Barlow lens will also come in handy here, and if your budget is tighter, a refractor telescope with an achromatic lens can give you a nice, sharp image. If you can, try to get 100x to 200x magnification for planet observation.
It’s probably obvious to you, but I’m going to give you the standard word of warning: don’t look at the sun through your telescope without the proper filters in place. Having said that, solar viewing can be an amazing experience with any telescope. Use a white light filter such as a Herschel Wedge to block the most powerful rays and give you a spectacularly clear image.
Deep sky objects such as star clusters and nebulae are incredible to behold. You’ll need a large aperture to gather as much light as possible, and a good line emission filter. You may want to think about taking the cost plunge on an SCT telescope, as well, for the best deep sky object viewing.
Once you spend a good amount of time behind your telescope, you’ll undoubtedly want to start taking pictures of your findings. Before you start, make sure you have a decent mount for your telescope. You’ll also want a lens with a wide field of view to help you locate the objects you’re seeking. Look for achromatic lenses and filters, as well, to make sure you’re getting the best image quality. Expect to pay a hefty price tag for the initial setup, though. A good telescope for astrophotography doesn’t come cheap.
There is a wide range of cost factors involved in choosing a telescope, but if you’re serious about getting into stargazing, don’t spend less than $100 for your device. You won’t get much quality from it, and you’ll just have to buy another one before long. Plan to spend around $200 to $300 on a decent refractor telescope, and more if you want specialty lenses. Reflector telescopes will bump you up into the $300 to $800 range, and an SCT will rocket you up to the $400 to $2000 range. These prices are for a middle-of-the-road telescope. You can certainly spend much more on a high-quality scope with a plethora of added features. But if you’re starting out, aim for the middle.
It would be a bit contradictory to buy a telescope blindly. Be sure to check the specifications of each model before you decide and consider how you’ll be using your telescope the most. Think about the longevity you want from it, too. If you’re a beginner, start with something simple and work your way up later. There’s no need to drop a huge bundle of cash on a device you’re not comfortable with. Once you make the big decision, make sure you keep your telescope clean and covered when it’s not used, and keep those lenses protected to avoid scratches. Treat your telescope right, and it can last you a lifetime.
Header image credit: picryl.com & Pixabay
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