AF Reflex 500mm f8. When released Minolta had seemed to have done the impossible. They had created a fixed f8 aperture lens that could auto-focus. The 500mm reflex (aka mirror) is not like other Minolta primes. Its design allows for an extremely light and compact 500mm lens.
The draw back is that it is f8, so will require good light and in the out of focus areas, point lights will appear as a torus shape i.e. doughnut. This effect can be pleasing in some limited situations, in others will not be detectable and in others can ruin a otherwise good image.
Many Minolta compatible lenses are available with the same specs but under 3rd party names such as Soligor, Walimex, Samyang, Prospec et al. I have read a few reviews here and there about them, but none make them out to be with their price. If you do buy one of these off-brand 500mm mirror lenses make sure they come with an iron-clad return policy.
This lens has been re-released under the Sony name but it is the same as the Minolta design. It is the only affordable AF 500mm lens.