For the Milky Way images, I wanted to re-install the TopazDenoise filter (I used them before on a different laptop but didn't install them on this one).
I downloaded them again and installed them. But when I opened up Photoshop, they weren't there. I restarted Photoshop, then all Adobe apps (Lightroom, CC Update...) and finally the laptop. But no luck.
I checked in my filesystem and under C:/Program Files/Adobe/Adobe Photoshop CC 2015/Plug-ins, I found a link to the Topaz plugin.
Then I searched on the Topaz web site and found instructions how to install the plugin manually on Photoshop 2015.5 (copy the plugin to C:/Program Files/Common Files/Adobe/Plug-ins). Tried that, restarted everything - still no luck.
Searched on my disk again and found another Plug-ins folder under C:/Program Files/Adobe/Adobe Photoshop CC 2015.5/Plug-ins. Copied the plugin there. Restarted and: voila!
... who in his right mind came up with the Photoshop version 2015.5 ???!!