Is there a reason that you've never candled? I'm a candling junkie, I have all the charts from each hatch with all the info I gathered from candling.
I wait until it's dark, turn off all the lights in the house and candle with an LED flashlight. I find it works best if you shine the flashlight through the end with the aircell while the egg is on the side.
Not sure why I never felt the need to candle. Maybe I'll try it tonight. Will it work this far along?