I'm clearly not yet an expert on candling. I have 58 eggs cooking. On day 4 I candled & guessed all but 2 were duds! Ha. So I waited 4 more days. This time - some of the eggs you could clearly see a shadow swimming around in there on several of them. In fact most of them I thought were duds before had a good sized shadow. I culled 10 eggs though -they looked clear - well most of them did. I left 3 or 4 that I just couldn't tell in the bator - the rest all looked good. Anyway - I decided to check my accuracy on candling by opening the culled eggs. 4 had started to grow - 6 had broken yolk or no fertilization. Of the 4 that had started - 1 was nothing more than a single red vein. 3 however had little bug eyed still kickin chicks : (( It looked like the yolk was broken on all three - at least that is what I'm telling myself - the yolk poured out of the egg like water & the chick came out after. I'm telling myself they would have died anyway because of the broken yolk. But I still have 48 in the bator - & most of them look really good. Considering they were shipped in the cold & 1 box left outside in the snow by the post office (I still have all 10 of those in the bator though 1 was questionable) I'd say I'm doing OK. For my first hatch. In a home made incubator.