Refractor Telescopes
A refractor telescope uses a lens to gather and focus light. The first telescopes built were refractors.
Advantages
Refractor telescopes are rugged. After the initial alignment, their optical system is more resistant to misalignment than the reflector telescopes.
The glass surface inside the tube is sealed from the atmosphere so it rarely needs cleaning.
Since the tube is closed off from the outside, air currents and effects due to changing temperatures are eliminated. This means that the images are steadier and sharper than those from a reflector telescope of the same size.
