Newtonian telescope
A reflecting telescope design with a concave primary mirror and a flat secondary mirror at 45 degrees, directing light to an eyepiece on the side of the tube.
Newtonian telescopes are said to be relatively easy to build yourself.
He observed Jupiter's moons with a Newtonian telescope.
Named after Isaac Newton, who invented this telescope design in 1668. The Japanese term combines ニュートン (Newton) + 式 (style/type) + 望遠鏡 (telescope).