http://www.em-jay.net/t1/skyrotation.zip
changed $mj::skyrotationspeed to integer, can be negative too, default value is 50
update ticks are something like this:
Code:
rot = featurePosition + ($mj::skyrotationspeed * 0.01) * ((timenow - timelastupdate) * 0.001)
should fix the speeding issue but I didn't test much and only in single player