Quick comparison
A refractor uses a lens to gather and focus light. A reflector uses a mirror. Neither is better in every situation. Each has strengths that suit different observers.
| Feature | Refractor | Reflector (Newtonian) |
|---|---|---|
| Main light-gathering part | Objective lens | Primary mirror |
| Tube | Sealed | Open at the front |
| Cost per inch of aperture | Higher | Lower |
| False color | Possible in achromats; reduced in APO designs | None from the mirror |
| Maintenance | Very little | Occasional collimation |
| Typical strength | Planets, Moon, double stars, portability | Faint deep-sky objects, large apertures |
How a refractor works
Light enters through a large glass lens at the front, which bends it to a focal point at the back of the tube. You look through an eyepiece at the rear. Because the tube is sealed, the optics stay clean and settled, and the telescope is ready to use quickly.
A common drawback is chromatic aberration, in which different colors of light focus at slightly different points. In inexpensive achromatic refractors, this can appear as a colored halo around bright objects such as the Moon or Jupiter. Apochromatic refractors use special glass or extra elements to reduce it, but they are costly.
How a reflector works
A reflector collects light with a concave mirror at the bottom of the tube. A smaller flat secondary mirror directs the light out the side to the eyepiece in a Newtonian design. Since mirrors do not split light by color, there is no chromatic aberration from the primary.
The central secondary mirror and its support do block a small part of the light path. In practice, this has a modest effect on brightness, though some observers notice a small loss in contrast on planets compared with a good refractor.
Aperture and cost
Aperture is the most important single number for how much a telescope can show. Making a large mirror is cheaper than making a large lens of equivalent quality, so reflectors usually offer much more aperture at a given price. That extra aperture helps with galaxies, nebulae and star clusters, which are faint and benefit from more light.
Image quality on planets and the Moon
Well-made refractors are widely admired for crisp, high-contrast views of the Moon and planets, as the light path is unobstructed. Reflectors can also show planets very well. Larger reflectors can reveal more detail, provided they are well collimated and have cooled to the outside air temperature. Can you see planets with a reflector? Yes. Jupiter’s cloud bands and Saturn’s rings are visible in a modest reflector, and sky conditions often limit the view as much as the telescope does.
Maintenance and day-to-day use
- Refractors: Sealed tubes mean little upkeep. They are often easy to set up and carry, especially small models.
- Reflectors: Mirrors can slip out of alignment. Collimation is a simple routine once learned, and many Newtonians have tools or screws designed for it. Open tubes also gather dust over time, though occasional dust has little visible effect on the image.
Reflectors, especially large ones, also need time to reach thermal equilibrium. Allow a while for the mirror to cool before critical viewing.
Disadvantages to consider
Biggest disadvantages of refractors: cost for larger apertures, longer and heavier tubes at larger sizes, and possible color fringing in budget models.
Biggest disadvantages of reflectors: collimation, bulk at larger sizes, and a more open design that needs some care.
Newtonian vs refractor: which is better?
It depends on your priorities. If you want something compact and low maintenance for the Moon and planets, a refractor is attractive. If you want to see as many faint objects as possible for your budget, a Newtonian reflector, particularly a Dobsonian, is hard to beat. For more on the simple-mount Newtonian option, see Cassegrain vs Dobsonian.
What about other designs?
Hybrid designs, called catadioptrics, use both mirrors and lenses. They are shorter and more portable. Read what a compound telescope is to learn how they fit between these two options. For a wider overview, see telescope types explained, or read what a refracting telescope is used for.
How to decide
- Choose a refractor if you value convenience, a sealed tube and sharp views of bright targets.
- Choose a reflector if you want the most aperture for your money and are happy to learn basic alignment.
- Whichever you pick, a stable mount makes a bigger difference to the experience than most beginners expect.