While browsing the astronomical web I chanced upon a site titled Observational Mishaps - Unusual Appearances at the site http://www.ciw.edu/vonbraun/obs_mishaps/images/appearance.html It is the second link that caught my eye, "earthquakes". Click on the link, take a look at the image and be certain to scroll to the bottom and read the Problem and Fix. Clear skies, aj -- See message header for info on list archives or unsubscribing, and please send personal replies to the author, not the list.