Guide to 50 UFO's
1) Zoom in just enough to see the detailed map type
2) Go to one of the corners
3) Start panning the map just quick enough so the colonies/ops don't have enough time to load. Just don't pan the map so quickly that you'll miss the UFO. If you just keep moving the map, even if it's the slightest bit but it just keeps moving nothing will load
4) Catch a UFO, since UFO's don't have to load they will stand out from an empty background.
5) Do this every hour
6) Celebrate your new achievement
Did it in step by steps because my English is getting so bad now and I don't know when to end a sentence -_-
Hehe took me less than 20 seconds after writing this to go and see if it still works ^_^
^^^ Detailed map meaning this sort of view. ^^^