from atlas 3rd Ed p144:
... about Charón is its unique polar orbit ...
... about 21 days to make this orbit, but it has many disturbing perturbations.
... every 149 days Charón is full and at Zenith in a given location ...
... every 10.2 years in certain locales near the equator there is a correspondence of perigee (closest proximity to Kulthea) and zenith in which Charón hangs huge and red over the night sky.
10.2 years are 170 cycle periods (350*10.2/21)
seams charon has a rather spiralling polar orbit in relation to kulthea,
so calculation of eclipses may be anything but correct
(need a canonical statement from TKA)
simplified:
we need to find a eclipse event in history and check against
the 149 day and 10.2 year periods of charon
vs the 70 day period of orhan from there