A telescope can be a big purchase, and you want to be informed before you drop your money on something that may not meet your needs. Below is a guide to help you make the most informed purchasing decision based on usage, needs, and the quality you want.
A refractor telescope uses convex lenses to harness light, magnify it, and deliver it to your eye. The objective lens (the main lens) captures the light and is nabbed again by the eyepiece lens at the light’s focal point. You can get a nice, clear image of the moon or our solar system’s planets, but deep space images will be less clear. A common complaint about refractors is an anomaly in the image quality called chromatic aberration. This is because blue light is refracted more than red light, which means you get layered images with blurred halos around the edges. The problem is fixable, though. Some refractors come with built-in achromatic or apochromatic lenses, or you can purchase these lenses to replace your objective lens. This can get expensive, but if a refractor is best for you, it’s probably worth the investment.
Reflector telescopes don’t use lenses at all. Instead, they use convex mirrors to reflect light. When the light travels down the telescope’s main tube, it’s reflected on a second mirror, which bounces the image to the eyepiece. This style is called a Newtonian Reflector (other, less common variations exist, too), and is better for deep space viewing of galaxies and other far objects. Most reflectors have built-in parabolic mirrors, as they are much more cost-effective. But these mirror types can cause image distortions called coma aberrations. Asymmetric light rays cause these distortions, which can create elongated shapes with a fuzzy comet tail effect. Stopping down your telescope (decreasing the aperture size) can correct this, or you can purchase a coma corrector to do the job. You’ll also want to keep your mirrors clean to avoid any damage from particulates.
If you can’t decide between the two, the answer may lie in a Schmidt Cassegrain telescope (SCT). The SCT uses a combination of refractor lenses and reflector mirrors to bounce the light inside the tube, essentially “folding” it. This means your tube will be shorter. When light enters through the Schmidt lens, it hits a spherical mirror, goes back up the tube to a secondary convex mirror, which then sends the light to the eyepiece. SCT models can often be computer controlled, which is perfect for astrophotography. The SCT also creates a sharper image, is ideal for either planetary or deep-sky viewing, is compact and portable, and nearly maintenance-free. Sounds too good to be true, but the kicker is, you’ll certainly pay extra for the quality.
The cost spread of each telescope style is vast. Reflectors tend to run in the least expensive range, with a good scope costing between $200 to $1,000. Because they need a bit of maintenance, though, you may find yourself replacing your telescope sooner than you would with another model. Refractors sit in the mid-range of $150 to $2,000 for a decent product. Specialty lenses, such as an achromatic lens, will jump your price to the higher end of the spectrum. You may find these more durable, but the quality of deep-sky viewing is diminished. The Schmidt Cassegrain telescope falls in the higher price range at an average of $800 to $4,000. Computerization and customized options will land you in the higher end, while the lower range will still give you a high-quality scope.
Related reads: An overview of the different types of telescopes
It’s important to ask yourself how you’ll be using your telescope before you buy one. If you’re planning to spend most of your time moon- or land-gazing, a refractor is better. If your interests are in deep space, you’ll want the more powerful capacity that a reflector offers. If you’re a photographer, or if you’re long past amateur stargazer status, it’s probably time to take the leap with an SCT. Either way, stargazing is an enriching pastime, and owning any telescope will offer you endless fascination.
Header image credit: AstroHurricane001, Wikimedia
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