At least, for
aiming at your "true south sat", leave the motor elevation set to your latitude. Only change so called "declination angle" by moving a dish up and down.
There have been reports that with 90cm dish, scale on dish bracket may be off, probably, because the same bracket is used for both 80cm and 90 cm dishes, and they have different offset angles, PLEASE, READ THIS THREAD:
http://www.sadoun.net/forums/install...highlight=90cm
Also, ou can do search on this forum for "90cm".