and high degree of integrity, makes it unique in Australia. Amateur built telescopes of this size (24") with professional grade mountings are still a rarity. There are no other examples of amateur built telescopes in NSW. The only older example in Australia is in Victoria at the Ballarat Observatory. The commercial 30" (762 mm) telescope at Linden is the largest publicly accessible instrument in Australia. The observatory is the closest to Sydney to still have good "dark sky" viewing for most of the viewing field, and the site is used regularly by amateur and semi professional observers for this reason. Sydney observatory, by comparison, has been rendered unusable for all but the brightest objects by light pollution from the city. The 24" (610 mm) reflector at University of Western Sydney is a modern commercial instrument, but its location also makes it prone to light pollution. The planetarium instrument located at the observatory is an extremely rare example of an Australian made planetarium on this scale in Australia, and perhaps the world. No other sites of this kind in NSW have the high degree of integrity and completeness of the collection associated with the design and construction of the instruments. The complex is rare in terms of the collection of tools, machinery, parts, work samples and other material relating to the production of telescopes and optical instruments during WWII. It is unlikely that any comparable site exists. The place is important in demonstrating the principal characteristics of a class of cultural or natural places/environments in New South Wales. The Linden Observatory is of State heritage significance because it houses a collection representative of the art of astro-mechanical, optical and other engineering from the 1930s to the 1950s. The extent of the collection, its condition and quality is unique. The variable star observations for the Flare Star program, and supernova discoveries made at Linden are typical of the work contributed by amateurs. Being a "dark sky" site provides much more potential for high level amateur or semi-professional work to be done at Linden than exists at Sydney Observatory. The Linden complex is very comparable to the home of the Springfield Telescope Makers "Stellafane" in America. This is a collection of buildings and telescopes on a parcel of land at a similar altitude to Linden, also established around 1920–30. "Stellafane" is listed as a National Historic Landmark for its pioneering role in the