The subject of ghost images, glare spots, false light, parasites and veiling glare has been summarized in photographic manuals (Ref 1) and has received wide attention in artistic, commercial and technical photography. In astronomical photography the matter depends entirely upon the astronomer's demands and the problem can be either crucial or trivial..
Jorge E. Simmons,
"Parasite Images General Considerations And Design Precepts", Proc. SPIE 0044, Instrumentation in Astronomy II, (1 September 1974); doi: 10.1117/12.953947; https://doi.org/10.1117/12.953947