The difficulties faced in using ground based telescopes due to which it does not make good quality observations are:
- Intensity of light rays reaching the Earth's surface decreases as some of the light is absorbed by the atmosphere.
- The change in atmospheric pressure and temperature cause the light rays to change their path slightly and thus shake the position of the image.
- We cannot use optical telescopes during day time because of the presence of sunlight.
- Even in night, city lights and cloudy weather can cause hindrance in observing the heavenly bodies.
To overcome the above problems, telescopes are now being erected in space itself. Some of the telescopes in space are:
- Hubble telescope: It is an optical telescope launched by the National Aeronautics and Space Administration in 1990. It is orbiting the Earth at a height of 589 km from it and has a mirror of diameter 94 inches.
- Chandra: It is an X-ray telescope launched by the National Aeronautics and Space Administration in 1999. Special mirrors which can reflect X-rays are used in this telescope.
