[Jun 15: Further quakes of 5.6 and 6.3 on Jun 13, 2011 have
finished off the station. Work had begun on taking the station to
pieces with a view to evnetually rebuilding. Rebuilding may still
happen, but it will be a while. In the photo below, X marks where I
think the cache is/was.]
[Mar 4: the station will have to be demolished. Disabling for
now.] On Feb 22, 2011 there was a 6.3 after shock centred
under Lyttelton. The timeball station sustained a lot more damage
(on top of the damage sustained in the 7.1 quake on September 4,
2010). 
I'm not sure of the status of the cache following the quake (we
are now based in Wellington, so I won't be able to check for some
time). It may be in a cordoned off area. If so, please do not try
to retrieve it. I'll see what the next log or two says, and then
decide whether I need to disable the listing, or maybe even archive
the cache.
The Lyttelton Timeball Station is one of only 5 in the world
known still to be working. It is a relic of another era in which
accurately knowing the current time (which is the basis of the GPS
system, with atomic clocks in satellites) was crucial in
determining the position of a ship at sea (to be precise, in
determining its longitude). I'm sure many geocachers will find the
station and its history to be of great interest.
The cache is in the grounds of the station, and is only
accessible during opening hours (10 a.m. - 5.30 p.m. every day
except Good Friday and Christmas Day). If you are there at 1pm you
will see the time ball drop. The grounds are free to enter during
opening hours. There is parking on Reserve Rd beside the station.
If travelling up Sumner Rd from Lytellton, watch the turn into
Reserve Rd; it is a very tight hairpin.
The cache is in a small plastic cylinder (berocca-type tube)
sitting in another container. It is in plain view, and can be
easily reached from the path.
The Timeball Station is a property of the New Zealand Historic
Places Trust. The cache has been placed with the kind permission of
the Trust.