Inconsistent Unit System and Model Orientation in Relation to Real-World Coordinates

[andreasfilipp]

We've noticed that the unit system and orientation of some models in the package are not consistently defined with respect to the real-world coordinate system. This lack of standardization is causing confusion and potential inaccuracies in usage.

Expected Behavior:
The unit system and orientation of all models should be consistent and accurately reflect the real-world coordinate system. This would allow users of the package to accurately model and analyze their data without the risk of inconsistencies or inaccuracies.

Actual Behavior:
The unit system and model orientation are inconsistently applied across different models in the package. This leads to confusion, potential inaccuracies, and makes the package less intuitive to use.

Potential Solution:
It would be beneficial to define a standard for the unit system (based on fits WCS) and model orientation in relation to the real-world coordinate system, and ensure this standard is applied consistently across all models in the package. It would also be helpful to provide clear documentation on this standard, to guide users in their utilization of the package.

[ConnorStoneAstro]

WCS is outside the scope of caustics, except possibly some helper functions. I think the model orientations are all consistent/standard. Adding some clear documentation would be great, perhaps a jupyter notebook explaining basic coordinate transformations?