There are some images in which the superlaser dish of the Death Star appears in the southern hemisphere, not the northern hemisphere as it usually does. Why is this?
Note: the idea for this question came from this site.
Unless the Death Star is very close to a planet or other massive body, any significant gravity it produces is artificial. As such, whether the laser dish is in the southern or northern hemispheres is purely a matter of camera angle.
Sometimes it looks like this:
Other times it looks more like this:
But in either case, the laser disk is in the same position relative to the ship itself.
Many shots are taken from the point of view of the ships flying around the Death Star, so that probably influences what the apparent orientation is, as is probably the case in the second picture.
So another answer might be:
It's always in the northern hemisphere. You're upside down.
The Emperor's throne room on the second Death Star was on the top of a 100-story tower located on the north pole of the superweapon.
The Emperor's throne room on the first Death Star was located in an observation dome at the top of a tower placed directly next to the station's superlaser. The platform served as Palpatine's watchtower in order to view the laser's firing demonstrations.
Subjectively, being poised to fire down on something is much more 'menacing' then just firing at it.