I've made a few posts recently about the Matte Painting's from Buck Roger's in the 25th Century and Logan's Run. Well here is an example from the original Battlestar Galactica movie of how not to do a Matte Painting. This really is one of the crummiest attempts at a Matte Painting I've seen, there's absolutely no blending edge or colour balance on any of the elements that have been added, the whole things looks like it was painted on a piece of cardboard and some holes were cut into with a pair of scissors for the live action to be added to. I always thought the perspective on this picture looked wrong too, it's because we appeared to be looking down on the Galactica crew and the Ovion's but across the way we could see Ovion's meant to be in caves that looked at a different angle and the caves didn't really have any depth to them.
I spent 15 mins messing with this Matte in Photoshop this afternoon removing the 2 caves and blending the pic a little better, not brilliant by any stretch of the imagination but it shows how much easier it is to blend stuff like this in post.