The TDM Encoder from Explore Scientific is part of their Telescope Drive Master (TDM) system which reduces drive errors inherent in most motorized mounts, which is critical during long-exposure astrophotography or astro-imaging. Use this encoder as a replacement, spare, or to have a separate encoder set up with a different imaging rig to swap equipment easier and get imaging faster. Mount-specific adapters are required to connect it to the telescope and are offered separately.