satellite that you can "see"? Or satellite that you can receive?
In theory, as stated above, it's 131W, and on the western side, it's 72E (Intelsat 22). But 131W covers only North America... So the Easternmost satellite that can be received in Sydney is likely 177W for C-Band. As for Ku, Satstar.net lists NSS6 @169W, but looks like Sydney is out of footprint and I don't know if that sateliite is still active at all. More likely, 180E is the easternmost Ku sat receivable in Sydney