any crown assembly movement apparatus disclosed herein moves the base 230 and the crown assemblies 221 222 down within the derrick 210 fig9 c illustrates a lowered position of the base 230 and crown assemblies 221 222 within the derrick 210 fig1 a 10c illustrate the application of the present invention to dual activity rigs e g as disclosed in u s pat nos 6 068 069 6 047 781 6 085 851 6 056 071 and 6 443 240 u2014 all incorporated fully herein for all purposes a system 300 includes a drill ship 301 a hull 309 and with a multi activity derrick 340 which is located above a moonpool 334 the multi activity derrick 340 drawworks 341 two present one shown in fig1 b with appropriate cable 344 and sheaves 346 350 traveling blocks 352 354 etc the derrick 340 is on a drill floor 314 first and second mini derricks 332 and 334 on a base 336 are movable down within the derrick 340 by movement apparatus 360 shown schematically may be any movement apparatus disclosed herein for moving a crown assembly fig1 c shows the position u2014 in dotted line u2014 of the mini derricks once lowered within the derrick 340 other apparatus equipment and structure in the rig 340 which is not labeled or named is as.