It’s essential to measure temperatures when baking sourdough.
I’ve been using this thermometer for many years. It is called a Mini RayTemp is held-held and has a trigger that you pull with your finger to start sensing. The backlight LCD display and auto-off to maximizes the battery life. The distance to the target ratio is 12:1, so that is, for a 1″ diameter measurement area, So my advice is to hold the thermometer should be held 12″ away; for a 2″ diameter, 24″ and so on.
It is really useful to measure dough temperature as well as the oven temperature, and the temperature in your fridge, and especially useful to use in conjunction with the sourdough loaf record form.