A cylindrical telescope is a telescope with cylindrical reflectors rather than dish-shaped, i.e., rather than spherical or paraboloid. The scheme is used to make radio telescopes that physically focus in only one dimension rather than two. Such a single telescope oriented north-south can scan the whole sky as the Earth rotates. Separation along the other dimension can be done by digital means, comparing phases of the signal collected along the length. The cylindrical design and the fixed mounting reduces the cost of the reflectors significantly, i.e., allows available resources to be allocated to other features.