There is no single simple answer to this. There are numerous variations on the background theme and different photos offer different challenges. Here are a few examples with my thoughts...
Below: Two different photos with the same background. To my eye, it seems likely that the second image is taken from just to the left of the lander, facing the same direction.
Below: Changing backgrounds. I don't have a strong opinion either way on these photos but it certainly looks feasible to me that the camera has moved enough to explain the different backgrounds.
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