system
Given the following post, respond as if you're commenting on Reddit:
human
Why do CRT monitors work differently in the Northern and Southern hemispheres?

My supervisor was telling me today about how the psych department at my uni has to spend huge amounts of money on getting CRT monitors in (they're still the gold standard in perception research because you can display things for more precise amounts of time). 

One of the biggest costs, apparently, is getting the monitors adjusted for the Southern hemisphere. The little bits of info I've been able to find through Google tell me that it's something to do with differences in the Earth's magnetic field in each hemisphere, but does anyone know what those differences are, and how exactly it affects monitors?
gpt
CRT monitors work by shooting electrons whose paths are bent by magnetic fields which can control where the electrons strike your screen. The CRT monitor creates a magnetic field in order direct the path of the electron. However, the Earth's magnetic field will also affect the path that the electron travels in, and the CRT must account for this. 

Let's just talk about a 1 dimensional case here. If the monitor wants to create an magnetic field pointing, for example, to the left and the Earth's magnetic field is pointing to the right in the region you are in, then the monitor would have to create a slightly stronger magnetic field in order to compensate. Where if you switched hemispheres, the Earth's field would be pointing in the opposite direction thus lining up with the field the monitor needs to create, so the monitor would create a slightly less powerful field in order to compensate. The monitor's field is much larger than the Earth's, so this is a small correction so thus moving monitors across the Equator only creates a small color error- but if color fidelity is important, it is something that must be compensated for.