the observer and models declared within the file. Several show files are often strung together underneath each other in show production. Both .vl and .sf have ASCII equivalents for editing--.vla and .sfa respectively. These are converted to their binary equivalents by a utility built into the Digistar system, which also checks for errors within the file. Digistar II show files are programmed in a language related to Pascal. Further, Digistar II can run animation files, .af, with the ASCII format .afa. An animation file consists of several model files, grouped together and loaded as one object. The Digistar II can either select frames individually, or animate the entire file. Digistar II is able to convert Digistar show and model files. Similarly, Digistar 3 is can convert Digistar II model files, though it cannot, at this time, convert show files. Popularity Despite its limits, the original Digistar was well received by many planetarians, and has been distributed worldwide. Though it lacked the pin-point stars of opto-mechanical projectors, and the full-dome rendering abilities of the later Digistar 3, many planetarians consider it a good balance between the two, especially considering the novel capabilities of seeing heavenly bodies from any point in space and time. The Digistar line has an installed base of over 550 planetaria as of 2019. Terence Murtagh, past president of the International Planetarium Society, stated in 2000, anticipating Digistar 3's full-dome video, "I think the next ten years will see the most dramatic advances in all-dome presentations since the invention of the projection planetarium in the 1920s and the arrival of the electronic Digistar in the 1980s." The Digistar Users Group has been operating since the mid-1980s and consists of several hundred facilities that have installed Digistar systems. References External links .vla file format information Worldwide planetariums - projector info Planetarium projection Planetarium technology Computer graphics