Look very closely at the image above. Here, my camera is the GWX Gold F11 Flak Station, with AngularAngle = 75° and hence VFOV = 60°. I ask the game engine to render the horizon in the middle of the screen at 30° up and it almost succeeds. I ask it to display at 50° up by setting Elevation Min to -20° and it displays too low by more than a degree. Asking it to display at 10° up by setting Elevation Min to +20° and it displays too high this time by about a degree.
The game rendering engine is displaying correct information incorrectly.
This is the second type of distortion in SH3. Objects in the upper half of the screen display too low, while objects in the lower half display too high. The errors are only on the order of a degree or so, but it is enough to make celestial navigation difficult. Together with the strange interpretation of local Zone Time and Greenwich Mean Time by the game clocks, it is no surprise that celestial navigation has eluded us within the SH3 world. Together with the lack of a proper navigation map with latitude, longitude, and time zone lines, it seems that they didn't quite implement what was possible.
The good news is that this can be measured and corrected for in the usual way of correcting sextant measurements for altitude. It is similar to a refraction correction (but quite different).