ABSTRACT
For example, stellar magnetic fields may be deduced from the polarization of the wings of spectrum lines (Section 5.2.3). The noise (errors, uncertainties) in the observations, however, will mean that a range of field strengths and orientations will fit the data equally well. The threedimensional distribution of stars in a globular cluster must be found from observations of its two-dimensional projection onto the plane of the sky. Errors in the measurements will lead to a variety of distributions being equally good fits to the data. Similarly, the images from radio and other interferometers (Section 2.5) contain spurious features because of the side lobes of the beams. These spurious features may be removed from the image if the effects of the side lobes are known. But since there will be uncertainty in both the data and the measurements of the side lobes, there can remain the possibility that features in the final image are artifacts of the noise, or are incompletely removed side lobe effects.
