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For the most basic form of telescope (in radiastronomy, a single dish), its maximum resolution depends on the diameter of the collecting device (e.g., dish or mirror) and determines the telescope's ability to discern the smallest features. The telescope may still also be able to resolve large scale structure, but when forming an image, it cannot separate the large scale from the small scale features. It can only produce one picture of the object, with all levels of detail visible, down to smallest details possible, according to its resolution.
An array, on the other hand, can yield images that reveal either large or small scale structure without having to alter its total size. To accomplish this, astronomers use different portions of the total data obtained in a single observing run. One set of baselines reveals large-scale details, while the smaller scale features are imaged using data from a different set of baselines.
In summary, then, an array's spatial resolution allows scientists to extract different levels of detail about an object.
How Do Baselines Determine Spatial Resolution?
A simple relationship holds between baseline length and
spatial resolution. Long baselines permit high resolutions, and therefore
reveal smaller scale structures.
Small Scale Structure in M82
This image shows small scale structure in the galaxy, M82, and was obtained using data from only the larger baselines in the BIMA array.
JPEG Image (27K); Credits and Copyrights
Short baselines, on the other hand, result in low resolutions, and can therefore image large scale structures.
Large Scale Structure in M82
Generated from data taken during the same run, but from only the shorter baselines, this image shows large scale structure in M82.
JPEG Image (13K); Credits and Copyrights
With a total of 12 dishes, the BIMA array would comprise of 66 baselines. Also, its new configuration will provide for still longer baselines. Together these two features will translate into improved image quality and spatial resolution.
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