I use a mini mag light with a krypton or halogen bulb. It isn't bright enough to see the heart beating, but it works...
I put the eggs in the incubator, it was running anyhow. The eggs with an intact aircell are under a broody hen. I'll keep an eye on these two, if I don't see anything start I'll pitch them. I figured I'm not out a whole lot by trying, just the electricity to keep the incubator going a bit longer. I'm done ordering eggs for the year... now just waiting for my Silver Pied hen to start laying. She and my Black Shoulder (apparently split pied) are three this year. Last year he didn't have even the beginnings of a train, I set the eggs under a broody hen and one developed and hatched so I have a beautiful Silver Pied cock now. I am hoping to get a hen for him out of these eggs... Just can't wait to see what he'll have for a train! I really hope it's bi-color, I love those!