Forgot I posted this. :S
Thanks to everyone for looking and commenting.
David, I had the extender on there because I intended to capture the Moon setting over the ranges at 280mm focal length. It was too cold to bother with taking it off so just left it on. Because it was obvious that I wasn't going to capture what I had hoped for, I just set the lens back to its native 70mm focal length; with the extender, that brought it back to 140mm.
Not my finest hour, that's for sure.
H