Napping is a skill. Many people cannot nap even if they are sleepy. Measuring the time should help you optimize the timing. Optimally, your tiredness will not be visible enough to easily guess the optimum timing.

If you measure the time between night sleep and the nap, you will notice that the length is always the same.

In other words, this helps you figure out the timing of your circadian dip even on days when you do not feel tired.

Any suggestions?