Observational instruments refer to devices or tools used by scientists and researchers to make observations, collect data, and analyze phenomena in various fields such as astronomy, geology, meteorology, oceanography, and biology. These instruments can range from simple binoculars or telescopes for observing celestial bodies, seismometers for measuring earthquakes, anemometers for studying wind patterns, to complex devices like spectrometers, radar systems, and sonar equipment used in remote sensing applications. The main purpose of these instruments is to provide accurate measurements and data that can be analyzed to better understand natural processes and phenomena occurring in the universe or our planet.