The mkh 800, set to fig 8, seems to me to be on axis with either side of the mic pointing towards the source. Set to omni, it seems that the mic is on axis if the end of the mic is pointing towards the source. If I have it set to omni, and instead point one of the sides of the mic towards the source, I get a higher ratio of ambient sound. The other "in between" settings, seem on axis if the mic is tilted in between side and end according to whether they are closer to an omni or fig 8 polar pattern. This can be easily tested by speaking into the mic, hand held, going through the polar patterns, and tilting it.

It might be better to decide on the polar pattern before recording
than after, to be able to make make a concious decision as to whether the mic(s) will be picking up sound on or off axis.