Originally Posted by itsratso
most recipes i have seen have the OG listed. so if i have a similar assumed efficiency then the OG is the target gravity (if not just using the time method)?
Correct. The OG listed for a recipe is a target. By definition it's what you'll get if you have the right volume and hit the efficiency target. But often efficiency can be hard to predict, until you monitor your process a few times. predictable efficiency is much more important than high efficiency, but you should easily be able to get at least 70% efficiency with good process.
Also your target OG has nothing to do directly with which sparge method you use. Although, sparge method can affect efficiency. Also, stopping the runnings at a certain gravity is most often associated with fly sparging where the running gravity is changing continuously over time. The reason to stop at somthing like 1.010 is that it's an indication that mash pH could be getting high which can lead to tannin extraction. With batch sparging the runnings for a given batch should be about the same. And if you have relative few, but large batches your runnings won't go to a low gravity. Keeping the runnings at a slow rate is also associated with fly sparging where a fast runoff can lead to channeling and a reduction in efficiency.