A small reflector telescope usually is less useful than a small refractive telescope, especially when there is plenty of light, but when one needs a large telescope and there is not much light, then the reflector telescope can be made much lighter than the refractor and usually much larger. It also can gather more light which is very useful in astronomy.
It also does not have to pass its light through thick large lenses that absorb part of the light. What is more, it can reflect almost any kind of light, from microwave radio to ultraviolet, while it is difficult to make lenses for large refractor telescopes that do not absorb some kinds of light such as infrared and ultra violet.
There also are advantages when one wants to see in more than one wavelength (colour) of light. It is difficult to prevent the different colours from separating out when passing through a large lens, but a reflector telescope does not have this problem much.
It's a telescope,that uses reflectors for you to see the objective ;D.
The lenses used in reflector telescope is the concave lens.
A reflector telescope collects light with a mirror. The mirror is located at the back of the telescope and reflects the incoming light to a focal point where it is then collected by an eyepiece for viewing.
optical telescope
Reflector telescopes are cheaper to make than refractors of the same size than passing through it, only one side of the reflector telescope's Often a secondary mirror is used to redirect the light into a more convenient viewing spot.
A Cassegrain reflector
it is a reflector telescope
A single-mirror reflector.
Reflector.
A refractor telescope uses lenses to gather and focus light, while a reflector telescope uses mirrors to collect and concentrate light. Refractor telescopes tend to be more expensive and have less light-gathering capability compared to reflector telescopes. Refractors are also generally easier to maintain and have a sealed tube, making them less affected by dust or dirt.
The small mirror is a plane one reflecting a bundle of rays to the side of the main tube. That is a Newtonian reflector.
The Newtonian Telescope.