Actually, a small maglight works fairly well on those dark eggs. At least, it worked okay on the welsummer eggs I set. You can pick one up at Home Depot.
I candle my brown eggs at 7 to 10 days they are easy to see them developing then. I cull at first candle ten I recandle just before lock down and do my final cull.
no really they do i have a pointer that a year ago got bit by a rattlesnake and lived now he fights them its always so funny watchin him spare with the little slithering menaces