If in doubt, download interesting files as you find them. You might not be able to find them again for some time. Try sending yourself e-mail from that site or mark it for your personal list. Spacelink offers news, lessons, background information, images, and software. You designate the target and location and download the digital CCD images the next day.
Image enhancing software is available to educators.
There is also a large database of images for astronomy, earth science, and biology. The Jet Propulsion Laboratory, JPL, offers its own database of astronomical images. For Mac users with ZTerm, these images are a snap to download. Lessons, background information, and software are also listed. Painted Rock, Carrizo Plain Natural Heritage Reserve, Chumash cave paintings.