  We explore the use of the tangential component of weak lensing shear to
characterize the ellipticity of clusters of galaxies. We introduce an
ellipticity estimator, and quantify its properties for isolated clusters from
LCDM N-body simulations. We compare the N-body results to results from smooth
analytic models. The expected distribution of the estimator for mock
observations is presented, and we show how this distribution is impacted by
contaminants such as noise, line of sight projections, and misalignment of the
central galaxy used to determine the orientation of the triaxial halo. We
examine the radial profile of the estimator and discuss tradeoffs in the
observational strategy to determine cluster shape.
