Photons and antiphotons, because they are uncharged, are considered the same particle. But this criterion would lead to the same conclusion for neutrinos and antineutrinos. These elementary particles have nevertheless an opposite leptonic number. They are different elementary particles. Special relativity makes a completely symmetric description of elementary matter and antimatter, but it seems that the only exception are photons. If photons and antiphotons are the same particle, there will be no phenomenon of electromagnetic attraction. We analyze the differences between elementary particles and antiparticles under external interactions. We make the conjecture that the main form of electromagnetic radiation of matter is by the emission of photons, while for antimatter it is the emission of antiphotons. With this conjecture in mind, we make a design of a telescope for focusing antiphotons. The nearest objects to be detected will be antimatter galaxies. The complete validity of this conjecture might depend on an experimental basis but it opens a discussion about possible differences between photons and antiphotons.