I find your perspective on the transmission characteristics of these binoculars hugely interesting, as I, like you, am an avid observer of galactic nebulae. Such information is exceedingly rare. Scarcely any binocular reviews address the observation of emission nebulae in any systematic fashion.
That your comments are backed up by vast observing experience make them all the more valuable. In that vein, perhaps you would like to share some of your remarkable observations with this instrument?
Best regards, Christopher
PS: You mention changes on the 2nd hand market. Which changes do you mean? Docter disappearing?
during the last years, my observing sessions have concentrated on the galactic nebulae through the 15x85 binoculars, and through the 6" F/5 refractor. The smaller binoculars are just my companions, also to check the quality of skies, but I run an observing session with the 10.5x70 or smaller, a few times a year.
That said, my last obseving session has concentrated on southern Perseus and northern Auriga with the 6" F/5,
beyond the NGC/IC catalogs, and including also the "elusive" very large planetary nebula Sh2-216, I took because it is in the Sharpless catalogue.
It may happen after the winter season, that I will return to the galaxies. It is sometimes incredible what can be seen with the small aperture optics.
Regarding the 2nd hand markets in Germany, my impression is that the Docter Porro binoculars have been deployed recently by people looking for top performance on budget, even if the Docter optics are missing the hard antiscretch coatings, antifog, rain protection, G-shock resistance, etc.
But they give you 30 years warranty, so Docter must have been dead sure about the manufacturing quality.