## 4 Discussion  
Here, we formulate some practical aspects and recommendations based on our experiments, in situ and laboratory magnetic susceptibility determinations. Most of the building materials traditionally chosen for the construction of pavilions are, for obvious reasons, non-magnetic (it would never occur to anyone, for example, to use iron fasteners). However, a detailed check of the magnetic properties, as the above examples show, is often necessary. In addition, the question of the allowable distance for the use of one or another medium-magnetized building material is also important, as the example of the magnetization of concrete during its solidification shows. We believe that the determination of the magnetic properties of building materials should be an integral part of geomagnetic research related to the deployment of a new magnetic observatory. It is a must to check them. Moreover, with the advent of innovative materials with high wear resistance and relative cheapness and the desire to use them for the frame, walls, and floor of measuring pavilions, as well as in the design of pillars, the task of studying their magnetic properties, providing information about them, and supplementing existing practical guidelines for the deployment of magnetic observatories becomes even more relevant. In particular, the concrete magnetization phenomenon produces certain \begin{table}
\begin{tabular}{c c c} \hline \hline
**Measurement Period** & \(\sigma_{D,^{\circ}}\) & \(\sigma_{D,}\)**Minutes of Arc** \\ \hline I. 10 January–12 September 2018 (Single LED stripe) & 0.052 & 3.114 \\ II. 08 August–08 November 2018 (LED set) & 0.076 & 4.558 \\ III. 16 December 2018–01 May 2020 (Halogen light bulbs) & 0.040 & 2.423 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Standard deviations of absolute magnetic declination values measured at the Klimovskaya observatory for three periods related to different lighting conditions in the absolute pavilion. See the details in Figure 7.  
limitations for using concrete in pillar construction, mainly related to the need for building a fully non-magnetic upper part of a pillar and avoiding making an entire monolithic concrete pillar. We are convinced that the study of the magnetic properties of building materials for magnetic observatories should, if possible, be carried out not only with the help of a kappameter but also by estimating the direct magnetic effect (for example, using a proton magnetometer or a fluxgate sensor mounted on a theodolite for absolute measurements). After the pavilions are built, or even at particular stages of their construction, a magnetic survey of their interiors with a step of 0.3-0.5 m is necessary. Next, after the construction is complete, it is recommended to carry out an outdoor metal detector survey in the pavilion locations, as this will help to find some undesirable ferromagnetic elements left at the construction site. The measurement of the magnetic susceptibility of rocks in the practice of deploying magnetic observatories is mandatory in the case of outcrops of igneous rocks or the presence of their thick layers, according to geological data. In other cases, it is desirable. Further studies will imply the modeling of a magnetic intensity effect from a magnetized body and the development of recommendations for installing infrastructural elements (light bulbs, power supply cables, etc.) in the vicinity of magnetometers in pavilions, finding out critical spatial distances to them. For further development of guidelines for magnetic observatories, their construction and deployment, it is necessary to demonstrate not only examples of successful application of certain developments in this area but also some illustrative and instructive examples of failures, breakdowns and, in general, the consequences of neglecting the recommendations for the deployment of stationary geomagnetic observations.