You want to have the motor at ZERO. Point the whole assembly at what you think is true south, which as Iceberg said was 87.
Then, on your
Mercury move the dish to AMC 3, 87.0 W. Then tune to an active transponder and move the whole assembly dish and motor and all slowly back and forth until you find signal. You also might have to adjust your dish up and down. That dish from
Sadoun might be off on the elevation by as much as 5 degrees.
Once you find AMC 3, you want to move to the far east then the far west, and do the same thing with moving the whole assembly. As long as you are plumb, you may not have to adjust very much. 2 degrees left or right is another satellite, so your movements will be very small.