For an 0.8 ac 16'-17' deep pond try for a minimum of 3 CFM 10psi operational pressure. Your diffusers will require 8-9psi. Standard compressors for this task are rotary vane and rocking piston models. It takes 0.5 to 1 cfm to operate each single head diffuser. There are lots of threads in the Systems Questions Section that discuss DIY and package aeration kits. Also read through the Aeration section in the Common Pond Q&A Archives. Shape of the pond and ability of a diffuser to freely circulate from once central area to all areas will depend on shape of the pond. Two to three diffusers may be needed.
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92494#Post92494"..turnovers. Is that measurement based on the amount of air I pump in a day?"
Yes and no. Turnover rate, recommended of at least 1 per day, is based on how efficient the diffuser is. If you just blow air out the hose and make big bubbles it may take 3-5 days to create a turnover. The more water diffusers can move the faster the turnover. Vertex website has a graphic showing volume of water moved per diffuser style.
In smaller ponds than 1 ac, I personally like to oversize the system to produce a relatively quick turnover then shut the system off until the next day. Regularly resting the compressor allows it to last longer.
Run time each day actually depends on the BOD of the water body. BOD - biochemical oxygen demand. Practical - how fast the DO is consumed on the bottom.
Compressor working parts have a useful life span - depending on variables. A good quality compressor with adequate diffusers and 6-8 hrs operation per day should last you 20-30 yrs before the bearings go 'bad'. Air making rebuilds will be needed a couple time before the bearings wear out.