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## Creating The Basic Image

A radio synthesis telescope array does not actually produce images of the
radio sky at which it points, but obtains information from which such
images can be constructed. The data that radio telescope arrays collect are transformed into a usable format
for producing images via a complicated mathematical operation called a **Fourier Transformation**.
Taking advantage of powerful digital computers, a special form of this operation,
called the **Fast** Fourier Transformation (FFT), is used to reduce the time spent on
this otherwise very time-consuming computation.
Because FFT's require a great number of calculations, they require hours of
computation time. Using a standard engineering workstation such as Sparc 10,
it may take 14 hours to crunch the numbers. Running the same
calculations on massively parallel computer like the Connection Machine 5
cuts the computation time to less than ten minutes. As part of a
multicenter
radiosynthesis imaging project, efforts are underway to harness the growing power
of high performance computers in order to further
reduce the delay between data collection and imaging.

**FFT-generated image of the galaxy, Cygnus A : FFT**

This image was produced from an FFT computation. While the intense radio source, Cygnus A,
is visible, it is still not very clearly defined. An additional data processing step,
namely deconvolution, would help clean up the image.

JPEG Image (47K);
*Credits and Copyrights*

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*NCSA. Last modified 11/13/95*