Your methodology is probably the only way to attempt to correct it, since if you change the crop settings, you'll end up with possibly portions of 3 or 4 different "moons" displaying... might be shades of Jupiter or something...
- From what I remember, SH3 uses the upper left corner of an image, while SH4 uses the lower left. I would imagine that SH5 does similar when it comes to grabbing images like that.