There is a very similar question here Reciprocal Lattice of a non-bravais lattice, but I don't fully understand the answer, and the question is now obsolete so I feel that I should ask it again.
How can I derive the reciprocal lattice of the HCP lattice? It has two sets of nonequivalent sites, and can not be comprehensively described by its three primitive vectors. @delete000 indicated in the question above that HCP can be treated as "a hexagonal lattice with a base", so how can I derive the reciprocal lattice with that method? Thanks!