"Telestereoscope" is a rarely used term for a device that allows a viewer to see images in three dimensions. There are a few synonyms that could be used to describe this concept, including "stereoscope," "viewing apparatus," or "3D viewer." Another possible synonym is "virtual reality headset," which is a more modern term for a similar device that allows users to experience 3D or immersive environments. Additionally, terms like "holographic display" or "3D projection technology" could be used to describe technology that creates 3D images without the need for a specific viewing apparatus. Overall, while "telestereoscope" may be a unique and interesting term, there are many other ways to describe this type of viewing experience.