Physics
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21343105p&link_type=abstract
American Astronomical Society, AAS Meeting #213, #431.05; Bulletin of the American Astronomical Society, Vol. 41, p.264
Physics
Scientific paper
During the summer, 2008 Research Experience for Teachers, J. Paradis worked at the NRAO in Green Bank to collect and reduce data taken on the 43-m radio telescope to compare models of atmospheric refraction at elevations below 10º. Unlike optical telescopes, radio telescopes cannot use guide stars to overcome deficiencies in refraction models but, instead, need accurate refraction predictions. The GBT, for example, has a large aperture, observes at high frequencies and to low elevations, and requires a model that is accurate to a few arc seconds. Unfortunately, there is no radio refraction model that has been universally accepted, with some of the most common models differing by up to an arc minute at the horizon.
There are a number of advantages in using the 43-m telescope at 1 GHz to measure refraction using the Moon as a source. The telescope can observe to the horizon, the Moon's size closely matches the beam width of the telescope, and the Moon is bright enough to have its position measured accurately in under 30 sec. Most importantly, the equatorial mount of the telescope, when combined with the monthly changing azimuth of Moon rises and sets, makes it possible to disentangle telescope pointing errors from refraction.
So far we have not collected sufficient data for a complete analysis, but lessons for high school students have been developed that embrace the core concepts of the summers’ efforts. Using BUFKIT, a weather forecast program developed by the National Weather Service, students in physics classes determine the atmospheric refraction at different elevations for fictional radio and optical telescopes in upstate New York. Students are given a pre and post test assessment to measure understanding for a topic students traditionally find difficult.
This work was supported in part by the NSF-RET program
Maddalena Ronald J.
Paradis Jeff
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