Georg, could you please clarify some of your points?

You say: ‘Sodium lamps ... work at a rather high pressure, in order to have as much "pressure line broadening” as possible. ‘ At first I was puzzled at your apparently not knowing that there were different kinds of sodium lamps, for example LPS and HPS, which certainly do not both strive after pressure line broadening. Then you later referred to LPS in a different context, but not the context under discussion.

I cannot remember anyone asking about German lamps in particular, and you do not explain why you mentioned them in particular. You also said that ‘In Germany at least there is no "former use" of sodium lamps on streets, conrarily, they are used more and more.” No doubt. I have not been in Germany lately and am happy to take your word for that. No doubt as newer technologies come to the fore they will be used less and less.

However, the lamps under discussion were the vividly yellow LPS lamps, and you then say, surprisingly in the light of your foregoing statements: “The classical low pressure sodium lamps are phased out of use”. It is not clear in context why you denied the “former use”. Please explain. In particular please explain what it was that you seemed to intend to contradict, or if not, what you intended to say at all.

For my part, I do not think that the phasing out of the LPS is such a good idea during the period in question anyway. They were cheap, effective, long-lived, and very efficient in comparison to HPS lamps. They don’t seem to interfere with astronomy as badly as their rivals. They were not especially pretty, but I suspect that even today intelligent planning could make good use of a mixed system, with LPS in combination with other lamp designs. Granted, “intelligent planning” is a big ask... (On balance, for example because of improved lamp life, more recent advances, such as fully practical induction lamps or possibly LEDs might be better, but they were not available at the time I mentioned. In the long term there always is improvement, though the long term sometimes is very long.)