The antiferromagnetic perovskites have a simple cubic‐magnetic structure with nearest‐neighbor exchange interactions only. The perfect‐crystal Green functions can be easily expressed in terms of tabulated integrals, so that they are particularly suitable for making quantitative comparison between theory and experiment. This is done for exciton‐magnon interactions in pure crystals, and for magnons associated with impurities. Electric‐dipole absorption in the pure crystal can occur when an exciton is created on one magnetic ion and a spin deviation on its nearest neighbor. The resulting magnon sideband reflects the interaction between the exciton and magnon which are in close proximity. If the exchange between a pair, when one is electronically excited isJ′, and the normal exchange isJ, then satisfactory agreement with the experimental lineshape can be obtained forJ′=0.5Jin RbMnF3. The positions of localized magnons are calculated as a function of impurity‐host exchange, and compared with experimental results on Ni2+in RbMnF3. The symmetry of the defect system is also considered, showing that additional terms are allowed. The most important of these is probably electric‐dipole absorption in the far infrared, creating two localized magnons.