Refractor Telescopes Explained: Achromat vs. ED/Apo
A refractor telescope uses a glass lens at the front of the tube to gather and bend light to a focus, delivering sharp, high-contrast images with almost no maintenance. Your main decision is between an achromat (an affordable two-lens design with a touch of color fringing) and an ED/apo refractor (premium glass that nearly eliminates that fringing for the crispest possible views).
If you have ever looked through a pair of binoculars or a spotting scope, you have already used a refractor. It is the design most people picture when they imagine a telescope: a long, sealed tube with a lens at the sky end and an eyepiece at the other. Refractors are a favorite first telescope for good reason, and in this guide we will explain how they work, break down the achromat vs. ED/apo question in plain English, and help you decide whether a refractor is the right telescope for you.
How does a refractor telescope work?
A refractor gathers light with a lens called the objective, mounted at the front of the tube. As light passes through the curved glass, it bends (refracts) and comes together at a focal point near the back, where your eyepiece magnifies the image. Because the light path is a straight, sealed tube, nothing inside gets bumped out of alignment easily and dust stays out.
That sealed design is why refractors are so beginner-friendly. Unlike a Newtonian reflector, a refractor almost never needs collimation (mirror alignment). You take it outside, let it cool for a few minutes, and observe. For a fuller comparison of the three main telescope families, it is also worth reading our guide to catadioptric telescopes (SCT vs. Maksutov).
What is chromatic aberration (and why it matters)?
There is one catch with lenses: glass bends different colors of light by slightly different amounts, the same way a prism splits sunlight into a rainbow. In a simple telescope lens, the colors do not all meet at exactly the same focal point. The result is a faint purple or blue halo around bright objects like the Moon, Jupiter, or a bright star. This is called chromatic aberration, or "false color."
Everything about the achromat vs. ED/apo debate comes down to how well a refractor controls this color fringing. The more advanced the glass and design, the less false color you see, and the sharper high-contrast targets appear.
Achromat vs. ED/Apo: what's the difference?
Refractors are usually sorted into three tiers based on how they tame chromatic aberration:
- Achromat (achromatic doublet): Two lens elements made from standard optical glass. Achromats bring two colors of light to the same focus, which greatly reduces false color compared to a single lens. Some faint purple fringing can still appear on bright objects, especially in "fast" (short) tubes. Achromats are the most affordable refractors and the standard choice for beginners.
- ED refractor: Uses at least one element of "extra-low dispersion" (ED) glass. ED glass bends the colors more evenly, so false color is dramatically reduced. Views look noticeably crisper and cleaner, and the price sits in the middle.
- Apochromat (apo): The premium tier, using ED or specialty glass in a two- or three-element design to bring three colors to the same focus. Apos deliver essentially color-free, razor-sharp images and are the top choice for astrophotography, but they cost the most.
Refractor types compared
| Type | False color control | Best for | Relative price |
|---|---|---|---|
| Achromat | Good | Beginners, casual visual use, the Moon and planets | $ |
| ED refractor | Very good | Keen visual observers, entry-level imaging | $$ |
| Apochromat (apo) | Excellent | Astrophotography, demanding visual use | $$$ |
For most people starting out, a quality achromat is more than enough to fall in love with the night sky. You can browse the full lineup in our refractor telescopes collection.
What can you see through a refractor telescope?
Refractors punch above their weight on bright, high-contrast targets. Their sharp, steady images make them outstanding for:
- The Moon: Craters, mountain ranges, and the shadow line (the terminator) look tack-sharp.
- Planets: Saturn's rings, Jupiter's cloud belts and four bright moons, and the phases of Venus.
- Double stars and bright star clusters: Pinpoint stars with clean separation.
- Daytime and terrestrial use: With a correct-image diagonal, many small refractors double as spotting scopes for wildlife and landscapes.
Because aperture (lens diameter) is limited by cost and weight, beginner refractors are typically 60mm to 100mm across. That is plenty for the Moon and planets, but faint deep-sky objects like distant galaxies show up better in a larger reflector. If you are unsure how much aperture you need, see our guide to telescope aperture and why it matters most.
Which refractor telescope should a beginner buy?
A great starter refractor balances aperture, portability, and a stable mount. Here are three popular options at different budgets:
- Entry beginner: The National Geographic CF700SM 70mm refractor is a lightweight, long-focus achromat that keeps false color low and is easy for the whole family to set up.
- Step up with tracking: The Explore Scientific FirstLight AR80 640mm refractor with iEXOS-100 GoTo tracker pairs an 80mm achromat doublet with a computerized mount that finds and follows objects for you—a big help for both viewing and beginner imaging.
- More aperture: The Explore Scientific FirstLight 127mm achromatic refractor gathers noticeably more light for brighter planetary and lunar views, on a smooth alt-azimuth mount.
Refractor vs. reflector: which is right for me?
Refractors win on convenience, sharpness per inch of aperture, and low maintenance, while reflectors give you the most aperture (and the most deep-sky reach) for your dollar. A rule of thumb: if you mostly want the Moon, planets, and grab-and-go simplicity, a refractor is a superb choice. If chasing faint galaxies and nebulae on a budget is your goal, read up on Newtonian reflectors before deciding.
Frequently asked questions
Are refractor telescopes good for beginners?
Yes. Refractors are one of the best telescope types for beginners because they are simple to use, hold their alignment, need almost no maintenance, and deliver sharp, high-contrast views of the Moon and planets right out of the box.
What does "achromatic" mean on a refractor telescope?
An achromatic refractor uses a two-element lens (a doublet) that brings two wavelengths of light to a common focus. This sharply reduces the color fringing you would see with a single lens, which is why achromats are the standard affordable refractor design.
Is an ED or apo refractor worth the extra money?
For casual visual observing, a good achromat is plenty. ED and apochromatic refractors are worth the upgrade if false color bothers you on bright objects, or if you plan to do astrophotography, where their cleaner, sharper images make a real difference.
Do refractor telescopes need collimation?
Almost never. Because a refractor's optics are fixed in a sealed tube, they typically stay aligned for years—unlike reflectors, which need periodic collimation (mirror alignment).
What size refractor telescope should I get?
For a first refractor, 70mm to 100mm of aperture is a sweet spot: large enough for great Moon and planet views, yet still portable and affordable. Bigger aperture shows fainter objects but adds cost and weight.
Ready to pick your refractor?
Explore beginner-friendly options in our refractor telescopes collection and start your journey under the stars tonight.