Principles
For detailed information on specific designs of reflecting, refracting, and catadioptric telescopes: see the main articles on Reflecting telescopes, Refracting telescopes, and Catadioptrics.
The basic scheme is that the primary light-gathering element the objective (1) (the convex lens or concave mirror used to gather the incoming light), focuses that light from the distant object (4) to a focal plane where it forms a real image (5). This image may be recorded or viewed through an eyepiece (2) which acts like a magnifying glass. The eye (3) then sees an inverted magnified virtual image (6) of the object.
Read more about this topic: Optical Telescope
Famous quotes containing the word principles:
“Unless democracy is to commit suicide by consenting to its own destruction, it will have to find some formidable answer to those who come to it saying: “I demand from you in the name of your principles the rights which I shall deny to you later in the name of my principles.””
—Walter Lippmann (1889–1974)
“[E]very thing is useful which contributes to fix us in the principles and practice of virtue.”
—Thomas Jefferson (1743–1826)
“In child rearing it would unquestionably be easier if a child were to do something because we say so. The authoritarian method does expedite things, but it does not produce independent functioning. If a child has not mastered the underlying principles of human interactions and merely conforms out of coercion or conditioning, he has no tools to use, no resources to apply in the next situation that confronts him.”
—Elaine Heffner (20th century)