I keep my thermometer on the wall of brooder same side as heat lamp, so it reads about 5 F degrees lower than directly under lamp.
So add 5F to my temps.
I get Chicks from my local
TSC on Saturdays so they are 3 to 5 days old when I pick them up.
My latest batch came into the store Friday so they were 3 days old.
I adjust the temperature several times daily. I shoot for 90 degrees the first week.
85 second week, 80 third, 70 forth week.
I also observe their behavior and adjust as needed.
I raise them on my enclosed porch. It can get over 90 degrees during the day this time of year. I had to install a window fan with my latest batch of chicks.
So I actually turn off the heat lamp on hot sunny days.
I use a plug-in dimmer switch to control heat instead of raising and lowering. Much easier.
It actually makes the bulb last longer. I've raised 4 batches of Chicks over 5 years on the original bulb. I've had 3 spare bulbs in the basement for 5 years. GC