Astrophysics Flashcards
Ray diagram of astronomical telescope in normal adjustment
Define fo
Focal length of objective lens
Define fe
Focal length of eye lens (fo>fe)
Define angular magnification
Angle subtended by image at eye/Angle subtended by object at unaided eye or fo/fe
Diagram of Cassegrain, reflecting telescope
Charge couple of devices versus eye
-Quantum efficiency of CCD is 80% compared to 1% in eye
-CCD is detect wider spectrum of light (infrared, UV and visible)
-CCDs have smaller spatial resolution, so better for capturing fine detail
CCDs less convenient to use, but images can be stored
Minimum Angular resolution
The smallest angular separation at which two points can be distinguished
Rayleigh criterion equation
Cons of refracting telescopes
-chromatic aberration, glass will refract different colours by different amounts, producing an image at different points
-lenses need as little Imperfections as possible (such as bubbles)-can be expensive
-for large magnification lenses need long focal length, so will be expensive to house
Cons of reflecting telescopes
-spherical aberration, rays may reflect off of mirror and fail to converge on one point if it is not perfectly parabolic
-second mirror can block incoming light
Resolving power of telescope
A measure of how much detail a telescope can see
Describe radio telescopes and how they work
Benefits of radio telescopes
-Radio telescope dish made of wire mesh, which is easier and cheaper than optical reflectors
-shape and construction of the dish does not have to be as perfect compared to optical telescopes, as the radio waves are much larger, so less affected by small imperfections
