An instrument for viewing objects at a distance

One word substitute is Telescope.

Microscope: an optical instrument used for viewing very small objects, such as mineral samples or animal or plant cells, typically magnified several hundred times.
Telescope: an optical instrument designed to make distant objects appear nearer, containing an arrangement of lenses, or of curved mirrors and lenses, by which rays of light are collected and focused and the resulting image magnified.
Periscope: an apparatus consisting of a tube attached to a set of mirrors or prisms, by which an observer (typically in a submerged submarine or behind a high obstacle) can see things that are otherwise out of sight.
Kaleidoscope: a toy consisting of a tube containing mirrors and pieces of coloured glass or paper, whose reflections produce changing patterns when the tube is rotated.