Serious Eats - seriouseats.com

I agree with much of the first comment but not the grain alcohol part. The Italians always use grain alcohol when making Limoncello. Vodka imparts a flavor of its own that isn't very Italian in nature and vodka doesn't provide the kick that a proper Limoncello requires. This is the limoncello recipe that I use and it can be condensed to make the liquer in 10 days if absolutely necessary but I wouldn't recommend it.