Note: Flickr recently went through a massive server transition, and portions of the service are still being worked on. Among the problems is that mosaic thumbnails on Collections are not visible, which means my primary page here for showing groupings by year are missing those thumbnails. The links do work—only the thumbnails are missing, so you can still navigate into a year to view those photos.
A coworker brought his telescope to the office to catch a glimpse of Mercury transiting the sun. He started with a rig he and his son built for viewing sunspots, but somehow it wasn't quite working right. Instead, he simply turned the eyepiece lens toward a sheet of paper, and Mercury's silhouette immediately came into view.