Note the 8-year gap. A good article here:
http://articles.adsabs.harvard.edu//...00114.000.html
I note a half-degree separation from the Sun's centre for the 2020 event; that one will be close shave indeed. A Hα observation is still all but impossible. You're going to need a huge prominence. Or find a way to view the Corona - she'll be close enough to be seen against it.
What makes these events so interesting to me is the fact that the usual crescent phase changes into a very obvious annular phase. There appear to be few accounts from people who have actually seen it so I consider myself extremely lucky to be one of them (7 June 2012, 1.5° separation between the centres of the discs). It is a stunning sight and one of the best views I have ever had, of any target, through any telescope.
I'll hazard a guess that the next close one after 2028 won't happen until 2036.