I either have a book light I can fit through the vent holes or the best way is to shine a really bright light under the incubator. If the light is bright enough it lights up all the eggs at once! right now I have a overcrowded incubator, so minus the egg cartons it's pretty easy!!How do you candle from the outside?
Here is the light I found that works wonders.
I have no idea the brand name. Just it's really bright!!!