The returns don't just show as slow moving....I've witnessed, several times, windfarm reflections on a Watchman primary which showed as a large, solid contact appearing out of our overhead and tracking away at huge speed...we measured the intervals and worked it out as Mach 5 or so - most unsettling the first time, and we were wondering if the US Mil were doing something scary!!! When the engineers explained the real reason it was a bit of an anti-climax...