The problem with the dial back lights is....... they can read inaccurately....... and you don’t know it.

I’ve had a couple of customers torch pistons as a result.
Verified faulty light operation after the fact by comparing their dial back light vs a non-dial back light.
One of them was off about 17-18deg at high rpms.
Showed 38 deg at 6000rpm....... was really 55deg with a non-dial back light....... hence the burnt pistons.

I have one of the cheap red Actron non-dial back lights Jegs used to sell for $39.
I had a nice old chrome Craftsman non-dial back light I bought in like 1980 that disappeared one day, and the Actron is what I got to replace it.