  We present a method to simulate deep sky images, including realistic galaxy
morphologies and telescope characteristics. To achieve a wide diversity of
simulated galaxy morphologies, we first use the shapelets formalism to
parametrize the shapes of all objects in the Hubble Deep Fields. We measure
this distribution of real galaxy morphologies in shapelet parameter space, then
resample it to generate a new population of objects. These simulated galaxies
can contain spiral arms, bars, discs, arbitrary radial profiles and even dust
lanes or knots. To create a final image, we also model observational effects,
including noise, pixellisation, astrometric distortions and a Point-Spread
Function. We demonstrate that they are realistic by showing that simulated and
real data have consistent distributions of morphology diagnostics: including
galaxy size, ellipticity, concentration and asymmetry statistics. Sample images
are made available on the world wide web. These simulations are useful to
develop and calibrate precision image analysis techniques for photometry,
astrometry, and shape measurement. They can also be used to assess the
sensitivity of future telescopes and surveys for applications such as supernova
searches, microlensing, proper motions, and weak gravitational lensing.
