Bring the blueberries and lemon juice to a boil in a large saucepan over medium heat. Cook, stirring occasionally, for 5 minutes. Remove from the heat and pour through a fine wire-mesh strainer into a bowl, using the back of a spoon to squeeze out the juice. You can freeze the solids in ice cube trays and use for smoothies.  Stir 3/4 cup sugar and the blueberry juice mixture into the tea. Pour into a pitcher. Cover and chill 1 hour. Serve over ice. Makes 4 servings.