Since a few months, some activity is observed on Neptune. HST could image it clearly:
http://www.astrosurf.com/planetessaf/autres/neptune_2019/n2019-09-28_F763anim_HST.gif

http://www.astrosurf.com/planetessaf/autres/neptune_2019/2019-09-28-0735.7_2019-09-28-2158.6-HST-F763M-iduy22kgq-drz_MAP_legend.png

I analyzed all amateur images and a few from pros, and calculated ephemeris of two possible persitant spots seen by amateurs. 
These ephemeris are far from being confirmed, and if they were the corresponding spots could be not active anymore. 
Please find them there, I will update them if I can get some other relevant measures:
http://www.astrosurf.com/planetessaf/autres/neptune_2019/ephemeris/

Anyway, in case your are lucky enough to get a clear sky (here I get either clouds or fog), 
and a correct seeing, observe Neptune, and send me/here your images, they can be extremly useful !

ALPO-Japan Latest      Neptune Section