Refractor
Also called: achromat, apochromat, apo, ED.
A telescope that uses lenses: sharp, contrasty, low-maintenance — with no central obstruction.
Refractors are the classic spyglass shape. Simple two-lens achromats show some false colour around bright objects; apochromats (“apos”, often with ED glass) correct it. Small apos are superb for wide fields, the Moon and travel; large refractors become very expensive per inch of aperture.