I'm using the lnb off the 500plus on a 90cm dish to locate the 118 bird. Is it necessary to skew thr dish in this case since it is the only sat I'm looking for
He is not talking about skewing the LNBF.
He is asking about skewing the dish.
If it is a round dish it will not have any skew adjustments.
If it is otherwise and has skew adjustments then set the dish without skew.