Compensation was clear skies at dawn from the window-sill.
Inset with 80mm f/5 refractor + X2 barlow + PD camera,
A bit later-
Now had chance to look at the image sequence I took to investigate the “fake” Arcturus.
Here is one acquired 2 minutes earlier with Mercury still clear of the trees (and with a slightly different exposure) that I have left uncropped to show the “real” Arcturus. No sign of the fake one!