Review comments on the manuscript 10.5194/hgss-2024-2. "History of the Potsdam, Seddin and Niemegk Geomagnetic Observatories - Part 3: Niemegk”

H.-J. Linthe

The author tries to present a historical overview of the evolution of the geomagnetic observatory in Niemegk. This is part of the Potsdam Prussian Meteorological Magnetic Observatory activities. The location near Niemegk has turned out to be a suitable place for proper field measurements, and thus the observatory can look back on a long and continuous record. For this reason, the Part 3 contains significantly more information reflecting the development of the observatory over the years.

Besides these positive aspects of the article, it definitely would gain from a general revision. Suggestions in that direction are listed below.

General comments:

The article gives a rather complete account of the Niemegk observatory installations and activities. These detailed listings are valuable but make it partly difficult and boring to read. For the sake of the article, it is recommended to put a number of detailed listings into an appendix. In that case the information is preserved but does not blow up the article.

The article would gain by major editing and stream-lining of the language. There are not directly mistakes but getting the meaning of the sentences is not always easy.

Detailed comments:

Abstract: suggested changes

"The very well-known and outstanding scientists for geomagnetism, Max Eschenhagen, Adolf Schmidt, Julius Bartels, Gerhard Fanselau and Horst Wiese directed among others, in historical sequence, the three observatories."

"...and is currently still in operation, acting as the German reference observatory for geomagnetism."

Introduction: This is really too poor. The purpose of the Introduction is to bring the reader into the subject and animate him/her to read the rest of the article. Both these things are not fulfilled. Although there are earlier articles about Potsdam and Seddin, this article should be self-contained, shortly outlining the rout from Potsdam to Niemegk, without the need of first reading the other two articles. References to the earlier observatory locations should appear when they are first called out and not all together at the end. It would be good to give towards the end already an outlook on the success of Niemegk.

Sect. 2.0 describes generally well the activities for choosing the location near Niemegk. For the interested reader it would be good to see some registrations from Seddin and Niemegk from the overlapping years as Fig. 5, possibly plots of hourly or daily means over some common months.

Sect. 2.1: The description of the buildings is generally ok.

Sect. 2.2.1: The listing of the instruments is rather detailed and not instructive for a historically interested reader. The text as it stands is more suitable for an appendix. Rather than listing the technical details of the instruments, it would be more instructive to describe their purpose. The beginning of Set. 2.2.1 could read "The three theodolites for measuring the declination and horizontal intensity, as well as the oscillation box (add the purpose of that box) found suitable conditions in the new absolute house, due to the large number of the 14 pillars. Two Earth inductors together with their galvanometer were also placed on separate pillars." (shortly outline the purpose and working principle of the inductor)

Continue the description of relevant instruments in this way. Drop their specific names here. Rather add their function in the context of an observatory. Are all the intermediate instrument developments of relevance here? Only those may be worth mentioning that harald new techniques of measurements and/or registration.

It might be interesting in this section to describe the technique of absolute measurements in the beginning of Niemegk and in comparison, the present technique with DI Flux and Overhauser magnetometer.

Sect. 2.2.2: The arguments listed above are also valid here. Rather than starting with the lamps, it would be more instructive to first describe the way how variations were recorded those days. Only after that it is clear why lamps and clocks are needed. Also here, the technical details are better listed in an appendix. When changes of recordings or instruments are described, it would be good to mention a reason or advantage of the new setup.

Is the mentioning of the vector proton magnetometer of importance here? Has it ever been used as standard instrument for the observatory recordings? Its description may well go into the appendix. Also its application at remote places is not actually needed here.

Rather, it would be more interesting to present the sets of official instruments for the field registrations and how they were operated separately for a few epochs, mentioning possibly in some words their advantages.

Sect. 2.3: Following the suggestions before, also here it would be advisable to start with the motivation for the two measurement lines and then follow with the technical description. Also for the following installation it would be interesting for the reader to learn a little bit about achieved magneto-telluric results derived from those measurements, e.g., accompanied by references.

Sect. 2.4: The heading may be expanded "Operation of the Niemegk Observatory and related activity at other locations". The first half outlines quite well the historical evolution of the observatory operation. Towards later times more and more sentences appear making plain statements, e.g. "In 1956 the precision mechanical workshop was moved from the basement of the ...". Such plane listings are more suitable for the appendix. Without mentioning a motivation or positive effect of such actions they are of no relevance for the reader. Similar arguments can be made for several statements.

Please add some words on the motivation for the activities at stations near the Baltic Sea and Erzgebirge.

Sect. 2.5: The last sentence of Sect. 2.4 would rather be a good start of 2.5.

Mention days and year of 50-year anniversary.

Sect. 2.8: The list of scientific achievements is interesting, but all these statements should be backed up by references. Mention also the years in which the findings were made. It is not a good sign, when no more recent developments after H. Schmidt are listed. Wouldn't e.g. the Potassium Magnetometer also be worth mentioning?

Table 2. Institutional affiliation of the....

Table 3: Heading better "Scientific Directors resp. Heads

References: The listing of all the Year Books would also be better placed in an appendix.

Figs. 1-4: The quality of the copies is not good enough. Text is hardly readable.

What is the difference between Fig. 15 and 16? Are both needed?

Fig. 24: The caption should be more instructive. What do we see? What is the purpose of the car? at which location?

The author has diligently recorded the developments of one of the best geomagnetic observatories in the world and it is a valuable record for the entire geomagnetic community. Facts, not commonly known by the community have been brought out here which shed light on the stages of moderinisation of geomagnetic observatories. The sources have been provided and due credits recorded.

However, a historical text is more than a record of chronological information.

The manuscript does not communicate the value of the developments at each stage, the technical and scientific dilemma which might have been faced, the interactions with scientists and engineers from other observatories, which were also developing simultaneously. Thus the text is a somewhat bland description of facts, which would be of little import to readers, who are not familair with the Observatory.

I suggest the manuscript be divided into three stages: Early, Stable and Modern and the developments and their significance of each stage be provided. Figures showing instruments and data of each stage, also personnel involved, should be included according to each stage. 

The scientific achievements need to be woven into the description of each of these stages, as these achievements are not independent, but are closely linked to the developments in improved data acquisition and processing. In this context, the stages of developments of data processing should be provided with equal emphasis.

The Niemegk Observatory is responsible for providing the Kp index, which are used by researchers within the community and also from allied disciplines globally. Only one line has been written on this, more information may be included as to why it was taken over from Goettingen University, what were further developments on this and how it has impacted the Observatory and the scientific world.

The Observatory also has collaborations and operations in several regions/countries of the world. A section should be included to describe these and the importance of the outcomes. 

The English language needs a very thorough editing. I started to make some comments but there are too many to annotate on the pdf itself. 

I recommend the author may realign the text and provide more scientific and social context to make it a valuable as well as enjoyable read.