It will be a slow affair (times below in UTC - add 1 hour to get UK British Summer Time):
(Monday 28 September 2015)
P1 12:12am : first contact (penumbra)
U1 01:07am : second contact (umbra)
U2 02:11am : third contact (total eclipse)
---- 02:47am : (mid-eclipse)
U3 03:23am : fourth contact (total ends)
U4 04:27am : fifth contact (partial ends)
P4 05:22am : sixth contact (penumbra ends)
The reason for the eclipse is identical with a solar eclipse: the sun, moon & earth all fall into line. On this occasion, the moon is on the other side of the earth to the sun & thus passes through the Earth's shadow, which causes the eclipse.
The centre circle above is the area of full shadow ('Umbra'), whilst the outer circle in the image above is the area of part-shadow ('Penumbra').
(The small horizontal line above is the ecliptic, which is actually the path that the Earth traces out against the fixed stars as it travels round the Sun)
In spite of the fact that the moon will pass through the umbra, it never becomes perfectly black. The earth's atmosphere bends light from the sun (just like light passing through water). The red end bends more than the violet, which tends to cause a blood-red moon at total eclipse.
--------- Alex Kemp