Grubb refractor telescope. This 27 inch refractor telescope was constructed at Dublin for the Royal Observatory in Vienna by Howard Grubb. Completed in 1878, it was the largest refractor in the world at the time. The Grubb company was begun by Thomas Grubb (1800-1878), an Irish engineer born in Waterford. The father and son company made as many as 21 refractors of 13 inch aperture or greater, as well as a number of reflecting telescopes of moderate size and many smaller telescopes. The Vienna telescope is now kept at the astronomical observatory of the University of Vienna.