That of, course, was what I was leading to.
Aerial rpm varies a lot from one make/type to the next, and that number would dictate how many paints would show, assuming they did.
Assuming some paints did show, the age of the tube would very likely affect the afterglow of each return.
If the aerial was not located on the tower there might have been some sort of obstruction in the direction of Erebus which could affect the coverage in that sector.