To add further confusion to all of this you can actually get far better resolution than the Airy limit or Dawe limit. The planetary imagers all work at about f/40 where the Airy disk diameter is about 50 microns! Yet they achieve the resolution of their sensor!
The answer is simple. The Airy disk has quite a sharp peak in intensity and they are actually imaging just the tiny peak that is above the noise. For a circular aperture it is in the form of a Bessel Function. All these tiny peaks are the data that leads to contrast in the planetary image.
See here
http://en.wikipedia.org/wiki/Airy_disk
All these black and white arguments need to be taken in the light of (excuse the pun) the signal to noise of the entire imaging system.
So for bright stars the resolution is far worse than the Airy limit as the bright star recorded image gets bigger with increasing star brightness as more of the weak maxima of the Bessel Function get recorded generally to saturation.
Dim stars and contrast in nebulae on the other hand actually can do as well as the sensor resolution.
Note these diffraction limits are for perfect optics. Most real imaging systems introduce what is called a point spread function. This can be reduced by Richardson Lucy Enhancement.
Remember there are only two rules in our Universe.
1. There is no FREE lunch.
2. If something seems to be to good to be true. It is NOT.
Bert