  Three-dimensional models of astrospheres have recently become of interest.
However, comparisons between these models and observations are non-trivial
because of the two-dimensional nature of observations. By projecting selected
physical values of three-dimensional models of astrospheres onto the surface of
a sphere that is centred on a virtual all-sky observer, these models can be
compared to observational data in different observables: the column density,
bremsstrahlung flux, rotation measure, H$\alpha$ flux, and synchrotron or
cyclotron flux. Projections were calculated by rotating and moving the
astrosphere model to the desired position and orientation and by then computing
the value of a given patch on the sphere by a modified line-of-sight
integration. Contributions to the selected observable made by all model cells
that are connected to the patch by the line of sight in question were taken
into account. When the model produces a bow shock, a distinct parabolic
structure produced by the outer astrosheath can be seen in every observable of
the projection, the exact shape depending on the orientations of the line of
sight and the stellar motion. Of all four examined astrosphere models, only
that of $\lambda$ Cephei shows fluxes that are higher than current
observational thresholds. This is due to the strong stellar wind and
interstellar inflow of the $\lambda$ Cephei model.
