Whenever you want exact center lattitude and longitude on Google Maps use following trick.

1. Keep proper zoom level, where you can see the exact location which you need to keep at center of map.
2. To take the location at center you can double click that location on Google Maps.
3. Copy following link, and paste it in address bar of same window and hit enter.
javascript:void(prompt('',gApplication.getMap().getCenter()));
4. You will be shown lat & long on messagebox wich you can copy.