HI Trevor,
The first thing that springs to mind is variable star observing. With only a little practice, an hour or so a week and equipment as humble as a pair of 80mm binoculars, you can be making a valuable contribution to the collection of scientific data on dozens of stars which is then in turn used by professional astronomers to plot light-curves and work out what is making the star tick.
With an 6" telescope there are probably several hundred stars you can monitor, or if you want to, as few as you like -- its up to you. There are never enough observers and they are always looking for more -- particularly in the southern hemisphere. There are lots and lots of stars that are being either neglected or only infrequently observed.
The training is simple, the materials cheap (almost free in the context of amateur astronomy), you'll learn the sky better than you could believe possible and you can do it all from the backyard!
For more info, get in contact with the AAVSO or the Variable Star Section in NZ
http://www.aavso.org/
http://www.rasnz.org.nz/vss/vss.htm
Best,
Les D