Differences
In contrast to radio arrays, the largest optical arrays currently have only 6 telescopes, giving poorer image quality from the 15 baselines between the telescopes. Most aperture synthesis interferometers use the rotation of the Earth to increase the number of different baselines included in an observation (see diagram on right).
Taking data at different times provides measurements with different telescope separations and angles without the need for buying additional telescopes or moving the telescopes manually, as the rotation of the Earth moves the telescopes to new baselines.
The use of Earth rotation was discussed in detail in the 1950 paper A preliminary survey of the radio stars in the Northern Hemisphere. Some instruments use artificial rotation of the interferometer array instead of Earth rotation, such as in aperture masking interferometry.
Read more about this topic: Aperture Synthesis
Famous quotes containing the word differences:
“When was it that the particles became
The whole man, that tempers and beliefs became
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Difference and were one? It had to be
In the presence of a solitude of the self....”
—Wallace Stevens (1879–1955)
“Quintilian [educational writer in Rome about A.D. 100] hoped that teachers would be sensitive to individual differences of temperament and ability. . . . Beating, he thought, was usually unnecessary. A teacher who had made the effort to understand his pupil’s individual needs and character could probably dispense with it: “I will content myself with saying that children are helpless and easily victimized, and that therefore no one should be given unlimited power over them.””
—C. John Sommerville (20th century)
“What strikes many twin researchers now is not how much identical twins are alike, but rather how different they are, given the same genetic makeup....Multiples don’t walk around in lockstep, talking in unison, thinking identical thoughts. The bond for normal twins, whether they are identical or fraternal, is based on how they, as individuals who are keenly aware of the differences between them, learn to relate to one another.”
—Pamela Patrick Novotny (20th century)