Not much help. A 7805 needs 2V headroom, so you can only throw away 3V from the 10V in the dropper resistor at the max current of 500mA. That moves 1.5W from the regulator to the resistor, reducing the max regulator dissipation to 6W - still a big heatsink. Even if you use an ideal LDO, you can only move 2.5W to the resistor. A better linear approach would be to split the dissipation between two cascaded regulators, a 7812 and a 7805. Both will need heatsinking but the worst case dissipation is only 4W for the 7812 and 3.5W for the 7805 so you can use two cheaper heatsinks. Below 14V, the 7812 will drop out of regulation, but it should still be capable of delivering 500mA with no more than 2V drop, leaving enough headroom for the 7805 at 10V.
However, a switched mode buck module is a *vastly* preferable solution, far more compact, energy efficient and cheaper unless you've got a free *big* heatsink.