Volume 459, Number 1, November III 2006
|Page(s)||283 - 290|
|Section||Celestial mechanics and astrometry|
|Published online||12 September 2006|
Monitoring and analysis of anomalous refraction using a digital zenith camera system
Institut für Erdmessung, Universität Hannover, Schneiderberg 50, 30167 Hannover, Germany e-mail: Chris.Hirt(at)web.de
Accepted: 1 August 2006
Context.Anomalous refraction is considered to be a limiting factor for ground-based astrometry in general and astrogeodetic observations in particular. Typical characteristics of anomalous refraction are basically known by means of spot-check-data, however the fluctuation is rather little studied.
Aims.The goal of this study is to derive empirical knowledge on the fluctuation of anomalous refraction in the optical domain.
Methods.A Digital Zenith Camera System usually applied for the astrogeodetic determination of the Earth's gravity field has been used for continuously monitoring anomalous refraction. With a sample frequency of about 2 observations per minute, about 7300 single observation epochs were collected during 6 nights. Residuals of the observations with respect to reference data show how anomalous refraction behaves.
Results.The analysis of approximately 70 h of observational data reveals heterogeneous fluctuation patterns of anomalous refraction at the zenith. Wave-like and bump-like variations appear as well as slowly-changing, drift-like structures. With respect to its magnitude, the effect reaches from 005 up to about 02 at frequencies of some hours. Even much lower frequencies of anomalous refraction are indicated in the data sets causing an offset of about 004. The accuracy of the filtered data has been found to be about 005–008.
Conclusions.The study indicates how anomalous refraction may fluctuate. The results are considered to give an estimate of the accuracy limit for astrogeodetic and other absolute ground-based astrometric observations.
Key words: astrometry
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.