1926: While the engineers at Zeiss still worked on the first model, a next generation was conceived. It should be free of constraints like invariable latitute. Instead, it would be an all-purpose device for any place on Earth and easily swing to Southern skies, for example. The objects below the local horizon would be masked by a bezel. The idea envisaged two separate star spheres, one for each hemisphere. It was realised by the dumbbell-design, the so-called "Mark-II". Each sphere scaled 75 centimeters in diameter and was connected by a bridge that enclosed the planetary projectors. This bridge was also the main axis mounted on a pivot. The design of the Mark-II should coin the appearance of the planetarium projectors for the next decades.

One peculiarity of this model was its mounting on a carriage and wheels. Maybe somebody thought of some kind of transportation, though, it turned out obsolete quite soon. 25 instruments were produced till the Second World War, the first one received the city of Barmen (today Wuppertal). Five projectors were sold to the USA and two to Japan. Other major cities in Europe also opened a planetarium with this model. Only 14 copies survived the War.