1/32K difference in flux corresponds to a roughly 1/32 millimag dip in brightness. Either I’m missing something important, which I do quite often, or I’d change “tough” into “a chance somewhere between nil and negligible”. That said, I’m a great fan of understatement.
In the ARPS meeting today we were advised, correctly in my opinion, to concentrate on objects with a transit depth of at least 10 millimags. Three hundred times deeper, in other words.
My experience is that good observations of a transit depth of, say, 5 millimags is achievable but not entirely trivial. I couldn’t manage one millimag.