chef's notes
Sugar can be reduced to 2 Tablespoons, depending on sweetness of melon.
Save time and buy packaged chunks of honeydew.
If a 9-by-12-inch pan is too large for your freezer, pour the juice into two 8-by-8-inch metal baking pans instead.
Granita can be made ahead. Once it is scraped, it will retain its light consistency. It may just need a quick stir before serving.