Equivariant maps between Calogero-Moser spaces

This is a footnote to earlier joint work with Yu. Berest, which constructed a bijection between the space of ideal classes of the Weyl algebra and a union of Calogero-Moser varieties. A key property of this bijection is that it is equivariant with respect to the action of the automorphism group of the Weyl algebra: the main result of the present note is that it is uniquely determined by that property.