Refractors are the type of telescope that most of us are familiar with. The tube holds the lenses in place at the correct distance from one another. The tube also helps to keeps out dust, moisture and light that would interfere with forming a good image. The objective lens gathers the light, and bends or refracts it to a focus near the back of the tube. The eyepiece brings the image to your eye, and magnifies the image.
Eyepieces have much shorter focal lengths than objective lenses.
Achromatic refractors use lenses that are not extensively corrected to prevent chromatic aberration , which is a rainbow halo that sometimes appears around images seen through a refractor. Apochromatic refractors are much more expensive than achromatic refractors. Refractors have good resolution, high enough to see details in planets and binary stars . Refractors are relatively expensive, if you consider the cost per unit of aperture. Because the aperture is limited, a refractor is less useful for observing faint, deep-sky objects, like galaxies and nebulae, than other types of telescopes.