To achieve seamless integration within Internet of Things (IoT)-enabled distributed observation networks, electro-optical telescopes must adeptly handle heterogeneous external guidance sources. In the routine operation of electro-optical telescopes, telescope control based on external guidance is one of the common functions. Telescope control systems need to have the ability to receive multiple external guidance protocols and guide the telescope pointing. According to operational requirements, the telescope control system will select an external guidance protocol to drive the telescope to bring the target into the field of view. This paper proposes an external guidance system with heterogeneous protocols compatibility which supports a self-verification capability. Specifically, it presents a modularized framework comprising three decoupled layers, namely the communicator, codec, and optimizer, facilitated by standardized interfaces to ensure enhanced scalability and protocol interoperability. We propose an instance of the optimizer with trajectory prediction function to integrate into the telescope guidance system, which is beneficial for bringing a target into the field of view and reducing the tracking jitter. Furthermore, based on the module reuse principle, two alternative channels are created, including a self-verification channel and an actual external guidance channel, with the selection depending on the usage scenario. The experimental results indicate that, compared with traditional external guidance systems, the design scheme proposed in this paper can reduce the lines of code (LOC) related to external guidance system by approximately 63.1%. Before deployment in the field, system developers can finish the self-verification work of an external guidance protocol and related functions to reduce the field joint debugging time. For common types of external guidance data errors, the optimizer has an outlier recognition rate of 98.2%, a false rejection rate for normal values of only 2.3%, while reducing average errors in guidance pointing, velocity, and acceleration by 31.3%, 40.4%, and 47.9%, respectively.