Teaching globular star cluster A picture is worth thousand words! How else would you teach Astronomy hobbyist important facts about globular star clusters in less than five minutes giving them a strong visual memory to aid in comprehending the wealth of information? The APOD image uses web technology to seamlessly combine two different shades of red on a glorious close-up of M71. The student only needs to move the mouse over the photo to see by himself or herself what space dust can do to light travelling through it. True, the picture needs words in order to pass the message. But these words do not hang in empty space but are directly associated with the photo of M71. It is much easier to remember the facts when looking at the cluster while reading about it. The main lesson from this effective teaching is better understanding of Color-Magnitude diagram which explains why the visible light arriving from a star needs adjustments before its real magnitude can be accurately defined. d...