is substantially parallel to the axis of rotation 15 a also the hub 15 can be made moveable relative to the processing unit 5 and or one or both arms 12 22 can be made extendable so that their length can be varied fig4 shows an elevational view of the embodiment of fig2 in this example the lithographic apparatus also comprises an interferometer 60 for determining the position of the wafer stage as can be seen in fig3 the interferometer 60 is in the way of the arms 12 22 of the robot 10 as they perform their rotation in order to avoid collision the arms 12 22 are generally z shaped with two horizontal parts at a different height and an intermediate part connecting the two horizontal parts as is shown in fig4 this way the arms 12 22 can pass the interferometer 60 during the rotation of the arms 12 22 such an adaptation of the shape of the arms as described above can also be used when other objects are in the way fig5 depicts a second embodiment of the present invention in this embodiment a processing unit 5 is also provided for processing substrates 1 the substrates 1 to be processed are supplied to the processing unit 5 by means of a transfer unit comprising a robot 110 the same robot 110 also takes processed substrates 1 away from the processing unit 5 a track 50 transports substrates 1 which are to be processed to the lithographic apparatus.