Hi Andy, the method I'm using (or variations of it) is crude but effective,
see here for the basic principle. Damian would not have caught the ring after June 2012 because there's been none to observe since then. No doubt he is preparing for this too.
I can't overstate both the
significance of the upcoming inferior conjunction, and the need to
play it safe. Next opportunity to see the annular phase after this one: 1 June 2028