Over a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, now known as anomalous refraction, is again being observed. Anomalous refraction is described as a low frequency, large angular scale motion of the entire image plane with respect to the celestial coordinate system as observed and defined by previous astrometric catalogs. These motions of typically several tenths of an arcsecond with timescales on the order of ten minutes are ubiquitous to drift-scan groundbased astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but never confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter scale slowly evolving coherent dynamical structures in the boundary-layer below 60 meters.
Level of Degree
Physics & Astronomy
McGraw, John T.
First Committee Member (Chair)
Second Committee Member
Third Committee Member
Refraction, Astronomical, Astrometry, Boundary layer (Meteorology)
Taylor, Malinda Suzanne. "On the sources of astrometric anomalous refraction." (2009). http://digitalrepository.unm.edu/phyc_etds/69