What causes star images to blur? How do astronomers correct blurring in telescopes?
1 Answer
Atmospheric turbulence the quality of materials used in the design of optical telescopes and the tracking accuracy of a telescopes mount.
Explanation:
For ground based telescope imaging of the night sky and stars, the trend amongst astrophotographers is the use of refractor telescopes. There are other types of telescope designs like reflectors and catadioptric that use either only mirrors or a combination of mirrors and lenses. They are generally used for deep sky viewing or planetary viewing.
Refractors contain glass lenses and one of the drawbacks is the phenomenon of chromatic aberration. This can cause distortion of point objects like stars and a purplish halo around them.
However this can be reduced by using higher quality low dispersion glass and special optical coatings in the design and manufacture of high end instruments.
Atmospheric stability and clear viewing is just as important to reduce blurring.
Nb a basic DSLR camera on its own with a standard 55 mm lens can also be use to capture incredible nightscenes but only for short exposures unless it is placed on an equatorial tracking mount to correct for rotation of the earth.
