Generally, you don't need to know the polarity, but I remember when there was a strong and weak satellite side by side, like just before the Spacenets got decommissioned, if you had tried to make up a name for a satellite that was not programmed into your receiver's memory (common problem), and if you picked a name that began with a letter that was part of a series of satellites of the opposite channel plan, and if you then put your receiver on "auto-tune", then when it nudged the dish even a degree to either side, it would determine that the adjacent slot was the slot you were really aiming for and misaim the dish.
As a practical matter, it doesn't matter for C-band which channel plan you choose, because once you peak the skew by rotating its probe 90 degrees if the polarity is wrong, most receivers will retain that offset setting for all the transponders of that polarity. As long as you manually peak for one horizontal and one verrtical, the offset setting will be incorporated for all of them.
It does help to know the SBS satellite channel plans, however. SBS 6, for example, only has 19 transponders on it, but they are NOT the lowest frequency transponders from the standard transponder plan, and it operates some of them as half-transponders, making them off-frequency. I had one Uniden receiver where, if I selected SBS 6, it would only allow me to step through the lowest 20 transponders and would misidentify some and not allow me to even reach others. If you need SBS 6 Ku, which, last I checked, still carried some analog sports backhauls, you should copy the transponder plan from lyngsat to help you find whatever you might be looking for.
