Star bright
Today I did a neat demo to show how it's possible to get information about stars from a photo. I first googled "star" and next to Brad Pit was this rather colourful (fake) photo of some stars, perfect. Download to desktop, open in Paint.net and sample the different stars. Shows very nicely how the ratio of red green and blue changes from star to star. Guess what, the blue stars have more blue in them. What's really nice is that the little RGB bar chart shows how the colours would lie on the black body spectrum curve, sometimes the peak is in the middle sometimes to the left and sometimes to the right.