The first rain since May might actually finally make it in this weekend...or at least cloud since it will be headed toward 3rd quarter and new Moon of course, so I fit in some Mars observing with the 20" in the red zone backyard tonight. (Hoping for the rain to finally put out the back country fires to the east of me that have wrecked DSO observing since August.) Mars and its moons have dimmed about half a magnitude since the peak of the opposition. It is 19.3 arc seconds across now, still quite large. Seeing was decent, good enough for 278x unfiltered at the start, but declined somewhat over the next hour or two.
Early in the session I searched for Deimos at 278x without any sort of occulting bar. Deimos was nearing greatest elongation, and I eventually picked it up in averted vision where it could be consistently located.. I had to wait nearly 2 hours before Phobos was nearing elongation on the other side of the planet. Whenever the seeing would sharpen I could detect Phobos on the edge of a diffraction ray, but there was enough fluttering to the seeing that I could not see it at 357x.
The main reason for doing this again tonight was to get a feel for how much Mars and its moons will have to have shrunk and dimmed before I can no longer catch them with the 20" in decent seeing in bright skies. It won't be nearly as close and large next time around at opposition in 2022, and it will be increasingly distant in 2025 and 2027 before it begins to slowly wend its way back in subsequent oppositions.
If you want to be ready for seeing the moons in 2022 at close approach of ~17.2 arc seconds, start practicing now to get an appreciation of what it will take.