I had fallen asleep in front of my computer (had been up since 5.00 am) and I think I was probably dreaming or at least still half-asleep when I submitted this. I must have had a senior moment, thinking I was doing the Herculis.
I received an email from AB this morning and have only just discovered that there was an answer. I am most grateful that someone took the trouble to answer what now looks to me to be a rather silly question.