Someone was recently looking for instructions for making a homemade candler. I ran across this site, which also has great pics of developing eggs. http://shilala.homestead.com/candling.html I candled my eggs this morning (day 6) and most look good-Yippee!!!!
A mag flashlight is a lot safer than what is shown on that site, which is full of useful information, but their candler looks to me like it would get dangerously hot. If you fashion a cone out of cardboard or even sheets of paper that fits over the big end of the flashlight and fits snugly over the end of the egg you will have a very good candler and if it has a led for a bulb, it will be VERY cool and you can inspect to your hearts content.