Although somewhat primitive, the electrotelescope was an electo-optical device that was used for surveying the surroundings. Electrotelescopes were once used on starships, but were phased out in favor of sensor arrays. Portable versions were still used throughout the galaxy for millennia since they had greater power and resolution than most electrobinoculars.
Electroscopes were electro-optical devices used to observe nearby planets, moons, and asteroids. Similar in concept to electro- and macrobinoculars but much more powerful, electroscopes provided a tremendous degree of magnification through the use of optics and computers that electronically enhanced existing light sources and reduced atmospheric haze and other sources of visual distortion. Electroscopes were equipped with sensors that scanned for energy emissions or communication transmissions, making even smaller models capable of detecting small freighters at distances of up to five light minutes, with larger ground or satellite based models having significantly farther range; as many were used as sensor backups for space stations and deep space observatories.
Electroscopes used a two-stage scanning system. The general scanning mode observed a large area, but with limited resolution and detail. When the control computer detected an anomaly or came across energy emissions that might indicate nearby starships, the electroscope’s detailed scan mode focused on the specified area to gather as much information as possible.
Most models featured controls and standard dataports and astromech droid interfaces. External comm transceivers could transmit data from a central base or link multiple units for composite imaging with tremendous detail.
Smaller units, such as the Neuro-Saav Technologies VXI-3 electrotelescope used by the Rebels on Hoth, could weigh as little as thirty-five pounds, and their repulsorlift generators allowed them to be moved easily. Larger electroscopes provided much greater resolution, but were so large that they had to be stationed permanently at an observatory, on a planet, or placed aboard an orbiting satellite.
Electroscopes often were installed as sensor backups for starports and space stations and were used on deep-space stations and observation stations for inhabited planets. Smaller colonies used these devices to scan for asteroids and comets that might be on collision vectors.
Since these devices were passive, only detecting incoming light and energy emissions, they could be used without fear of detection by passing starships. They were perfectly suited to the Rebel Alliance's and other outlaws' many outposts, such as on Tierfon, Thila, and Derra IV.
When the Rebel Alliance established Echo Base on Hoth, secrecy was vital to its survival. Active sensors or orbital satellites were out of the question; instead, the Alliance relied on over a dozen Neuro-Saav VXI-3 electroscopes positioned at the main base and at remote observations posts to provide an early-detection scanning system. Unfortunately, this network was hampered by the Hoth system’s numerous asteroids and comets, and a Viper probe droid managed to land on the planet undetected, alerting the Empire to the Rebel’s presence.