Wenn you know the exact time at a certain date that the sun is at exactly south (i use
Satellite Look Angle Calculator for that, with chosen "aimed satellite" exactly my longitude), then you can aim at exactly south.
Put some tape or a string from top middle of dish to middle of LNB, and the shadow of that should be exactly in the middle of the dish at due south time. If the sun is shining, of course...
After that, you can check if you follow the arc properly.
When the sun doesn't shine, or you're not at your dish at the sun-at-due-south time:
A.) with USALS motor:
- set the motor and /dish angles, and align everything exactly.
- then move the motor with USALS (with correct coordinates) to the satellite longitude of your choice.
- rotate the whole mount till you find your satellite.
This way your setup's south will be at due south, using a not-due-south satellite.
B.) with diseqc 1.2:
- set the motor and /dish angles, and align everything exactly.
- let some calculator calculate the "(modified) hour angle" from due south to the satellite of your choice.
- using the width measure of the dish: calculate how much movement forwards/backwards of the sides of the dish corresponds to that hour angle rotation (simple goniometry).
- move your dish to that position with your motor or actuator.
- then rotate the whole mount till you find your satellite.
This way your setup's south will be at due south, using a not-due-south satellite.
(I have an approximate calculator for the modified hour angle calculation (will try to make a precise calculator someday?), so I maybe can help with steps two and three above.)
Does this help?
BTW: Are you indeed using MODIFIED motor angles?
BTW2: There seem to be people that use the polar star for finding the due north/south axis.
As the polar star is not EXACTLY above the north pole, I would think this method might be not exactly accurate. But I've no experience with that.
And it doesn't take into account the modified motor axis angle, so that's not good also!
greetz,
A33