I candle when I take them from the mother, I also candle durning and about half way thru you can see the snake moving around. cool! also if you candle albino X het eggs you can tell which are albinos and which are hets. around day 30 give or take a few days the albino eggs will have a pink glow to them. and the het eggs are a lot darker. I would think you can also do this with lucy eggs. with a little luck, hopefully I'll know in a few months
I candle as they go into the incubator. At this time you can already see veins.
Then I candle every few days to watch developement. It's really exciting to me. About 7 days in you can see the eyes and body. About 14 days in they really start to move around and you can see the spine taking form. I use a LED light, very little heat is generated.