Daily Image
12-04-2007
The sun rising above the HBAs in Exloo
| Submitter: | Stefan Wijnholds |
| Description: | This movie combines all sky images based on snapshot observations with the 24 LOFAR high band antennas installed at the CS010 site at about 10:30 AM UTC over the frequency range from 110-230 MHz. It shows a very interesting transition occuring in the HBA frequency range. At the lowest frequencies the galactic plane, visible around the zenith oriented from East to West, is the most dominant feature while the sun, visible in the Southern hemisphere (to the left!), is a rather imperspicuous source. At the highest frequencies the roles are reversed and the sun completely dominates the image. This is mainly caused by the difference between the solar power spectrum, which is rising towards higher frequencies, and the galactic synchrotron spectrum, which is decreasing towards higher frequencies. Note that the Sun has a second image on the right (North), caused by well-understood grating lobe effects. There is much more to be seen in this image, and the author will be happy to discuss the wealth of interesting features in exhausting detail. Technical information: 16 antennas are arranged in a 4x4 1.25 meter spaced tile configuration, the other 8 antennas are placed in 2 straight arms along a line from South-East to North-West. The measurements were done on April 8 and 9, 2007 in the 170-230 and 110-190 MHz frequency band respectively. Each image is based on imaging with the array of x-dipoles on visibility data of a 4 second snapshot observation in a single subband at the indicated frequency with the station correlator. |
| Copyright: | LOFAR |
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