I agree with Tartan - consistency is better than precision for the vast majority of situations. If you plan on putting your quilt with star points into a judged show, then you can worry more about the precise quarter inch...but you can also find other ways to make it work.
Originally Posted by
Tartan
As long as you sew the whole quilt with the same seam allowance, it should be fine. It can be tricky to get it perfect but eventually it will come.