This page contains a somewhat eclectic collection of topics which do not appear to have a place elsewhere on the site. Some may perhaps be useful and others interesting. Please feel free to ignore anything which doesn't fit into either category.
Many modern amateurs like to observe, either visually or by imaging, globular clusters. Part of their appeal is the aesthetic attraction of the brighter ones. Another part is that fainter clusters can be very challenging technically. A further attraction is that, contrary to the expectations of many amateurs, globular clusters can be picked up far beyond the confines of the Milky Way galaxy; a few of them are visual objects in relatively modest telescopes and thousands are within range of well-equipped amateurs.
In an attempt to promote the observation of globular clusters I have created three challenges which may (should, in my opinion) be attempted by astronomers whatever their experience or equipment available to them. The Full and Restricted Galactic Cluster Marathons cover globular clusters which are associated with our own galaxy. The Extended GC Marathon is devoted to clusters in orbit around external galaxies.