GoForSmoke:
But you know... 1024 does allow near-instant integer division by a 10 bit right shift. And a rounded-down result.
That's what was in my mind when I started this ...
A better way to think about it is to imagine measuring 8 volts with an ADC that can return values of 0,1,2,3 or 4. There are 5 numbers in the range 0-4, if for example you are using them as array indices. However there are only 4 steps between 0 and 4 and the voltages represented by each ADC value would be 0, 2, 4, 6 and 8. The gap between those voltages is 2 or 8 volts divided by the number of steps.
Having said all that I will happily live with the small (0.1%) error caused by using 1024, in return for the mathematical simplicity. I'm not sure the ADC is that accurate anyway.
...R