I realized that there was an easy way to get the ring opening angle for the 28 Sgr ring occultation--just check out the Earth-based ring opening angle in the Saturn viewer for July 3, 1989. That number, at the midtime of the occ, was 25.40 degrees.
Just to make sure, I get the same number from the dot product of Saturn's pole with the star direction.
Note, of course, that the star was south. So the ring incidence angle was 64.60 degrees. The "north-based" ring incidence angle was 115.40.
I realized that there was an easy way to get the ring opening angle for the 28 Sgr ring occultation--just check out the Earth-based ring opening angle in the Saturn viewer for July 3, 1989. That number, at the midtime of the occ, was 25.40 degrees.
Just to make sure, I get the same number from the dot product of Saturn's pole with the star direction.
Note, of course, that the star was south. So the ring incidence angle was 64.60 degrees. The "north-based" ring incidence angle was 115.40.
--Mark