And now the section many of you have been waiting for. Of course, you could have scrolled down to this bit straight away if you'd wanted. The Earth's atmosphere causes sunlight to bend, especially so at the horizon where the apparent thickness is greater. In fact I last saw a tiny speck of the Sun at about 10pm Sunday 26th. The Sun was at least 2 degrees geometrically below the horizon at this point.
Nautical twilight lasts until the horizon is lost.
Astronomical twilight lasts until the brightness of starlight overtakes the indirect illumination of the sun. I believe that is when we can see stars of magnitude 5. Or we might say that at that point, it is without argument, dark. So, Civil twilight lasts until April 6, Nautical twilight until April 21, and Astronomical until May 9. The brightest star, Sirius, is also visible down here, but it is near the horizon so gets washed out by the sunlight for a longer period.