Passage: In 1880, Johann Palisa, the director of the Austrian Naval Observatory (538), was offered a position as an assistant at the newly completed Vienna Observatory. Although the job represented a demotion for Johann, it gave him access to the new 27-inch (690 mm) refractor, the largest telescope in the world at that time. By this point Johann had already discovered 27 asteroids, and he would employ the Vienna 27-inch (690 mm) and 12-inch (300 mm) instruments to find an additional 94 asteroids before he retired.Among his discoveries was the asteroid 253 Mathilde, found on November 12, 1885. The initial orbital elements of the asteroid were then computed by V. A. Lebeuf, another Austrian astronomer working at the Paris Observatory. The name of the asteroid was suggested by Lebeuf, after Mathilde, the wife of Moritz Loewy—who was the vice director of the observatory in Paris.In 1995, ground-based observations determined that Mathilde is a C-type asteroid. It was also found to have an unusually long period of rotation of 418 hours.On June 27, 1997, the NEAR Shoemaker spacecraft passed within 1,212 km of Mathilde while moving at a velocity of 9.93 km/s. This close approach allowed the spacecraft to capture over 500 images of the surface, and provided data for more accurate determinations of the asteroid's dimensions and mass (based on gravitational perturbation of the spacecraft). However, only one hemisphere of Mathilde was imaged during the fly-by. This was only the third asteroid to be imaged from a nearby distance, following 951 Gaspra and 243 Ida.

Question: How many inches was the refractor?
27