Koch, Andreas and Grebel, E. K. and Odenkirchen, Michael and Caldwell, John A. R. (2004) Correcting spatial gradients : the case of Wide Field Imager photometry. The Messenger, 115. pp. 37-39. ISSN 0722-6691
Full text not available from this repository.Abstract
We present a method to significantly reduce large-scale photometric variations seriously affecting imaging data from the Wide Field Imager (WFI). The primary source for these gradients is non-uniform illumination, which cannot be corrected by standard flatfielding techniques. Comparison of our observations with well-calibrated multi-colour photometry from the SDSS enabled us to characterize and quantify these variations and finally to model them using a second-order polynomial. Application of the model to our observations and an independent dataset consistently reduced the large-scale gradients and thus provides a generally valid and simple tool for improving WFI photometry.