BBT and night nursing

Hey all. I just started my cycle again and want to chart bbt for the first time. My question is, how much will it mess up if I'm not getting 3 consecutive hours of sleep before temping? In the process of going from two to one nighttime feedings with my 9mo, sometimes she wakes up once around 2:30 am and those nights I can probably get the three hours. But sometimes it's 1am and then 4 or 4:30 am and we get up at 6:30.

Curious what others experiences are!