Oops, WhiteStarLine stupidly wrote:

snip . . . like Iridium flash brightly for 15 seconds or so but
traverse one end of the visible sky to the other in that time . . .
/snip

Poor proof reading! I didn't really mean that they whizzed across the
night sky in 15 seconds, just that a typical low orbit satellite is
visible for a few minutes and in that time tracks across a significant
part of the visible sky.