The author's excellent 'powers of observation' [=ability to notice and pay close attention to things] are evident in the book's detailed descriptions.
The plants seem to have recovered from the disease, but they are still 'under observation'. [=someone is watching them carefully]
They're keeping him at the hospital 'for observation' [=so that doctors can watch him carefully] for another few days.
(..) All right. It's beautiful up here. A more perfect stage could not be asked for. I don't see any instruments. Your powers of observation continue to serve you well. But wait. It is to Madame Justice that I dedicate this concerto... ...in honor of the holiday she seems (..)2005 V for Vendetta
(..) following the function of what... ...and what I am is a man in a mask. - Oh, I can see that. - Of course you can. I'm not questioning your powers of observation. I'm merely remarking upon the paradox of asking a masked man who he is. - Right. - But on this most auspicious of nights... (..)2005 V for Vendetta