The refractor telescope has many advantages and disadvantages. One of the disadvantages is that the lenses are made of glasses therefore it has to be perfect with no air bubbles or scratches in the glass as this will impair the users viewing. Another disadvantage is that lense are weakest around the edges because they are thinnest there and that is the only place they are being supported by the telescope so this can lead to easy breakage. The lense can have colour distortion which means when white light goes through the lense it is split into colours. Since violet right is refracted more than red, the violet is brought to a focus clearer and this will make the image coloured and blurred, this is called chromatic aberration. Some advantages of refractor telescopes is that refractor telescopes are rugged meaning it is more resistant to misalignment than the reflector telescopes after their initial alignment. The glass surfaces don’t really need cleaning because it is sealed from the atmosphere this is efficient! The images are sharper, steadier and better than a reflector telescope because the tube is closed off from the outside and there will be no effects of changing temperatures or air currents.The focal length of a lense is proportional to the size of the image that is produced. Therefore if the focal length is longer the image will be larger. How bright an image will be also depends on how much light is collected by the telescope. The area of the objective lense is