Dont you just love it when...

 ...you get wonderful greyline spots like this (10MHz, FT8 (25W)).  There are actually two stations receiving me - W1YY and N7XR - on such a precisely the same path that they are only distinguishable on a very close zoom-in:

Skewed path

An interesting skewed path arose on 24MHz this morning.  Initially listening with the beam at 120 degrees, you can see how much weaker - by about 9dB - the signal became (top two time slots) when I turned to 160 degrees - the great circle path.  The explanation is almost certainly Es.

Intreresting article.

Not very new, but very interesting article on long-path propagation:

https://www.qsl.net/ik3xtv/ARCHIVIO/QEX%20JanFeb%202017%20Article%20%20a%20study%20of%20long%20path%20echoes.pdf