Thanks for your comment. While making the photo I was standing on a thick branch and used the possible maximum zoom, in extremely strong wind. ☺ I don't see the left part "invisibly" dark (it's obviously dark, anyway) on my screen; tried level adjustment through PP, but it didn't improve the image due to the bright parts. Anyway, at least for a few hours we had sunshine today, not only heavy rain and storm.
Kind regards, László