Hi Katie-
I read one a site that it is better to test twice a day because you could have a shift in temps and not know it and ovulate later then you thought.
I take my BBT at 7am every morning and at 10:30pm everynight. I then have two different charts to use and I can see when my surge will happen I have it pined down now. I will try to find the artical and post.
Hope this helps.
Heather C.
Swaying Pink for #3! Lowered PH to 5.5 and goal is 4.5, girl diet and tons of Crystal Light
My Ovulation Chart