Using your dates of Dec 4-11, you can visit Istanbul for $983 all-in on *A carriers (CO, LH, TK). If you play with the routing, you could get 7431 miles each way, for a total of 14862 eqms, going SEA-EWR-FRA-IST. However, if your mileage needs aren't that desperate, you could simply go SEA-FRA-IST, for about 12k miles round-trip.

I suggest is that you pay attention to the fare classes, because as a OnePass member, you won't earn 100% eqms on all LH flights.