December 6: Began to add descriptive captions to The Messier Catalog: Open Star Clusters.
November 29: In response to a question about the rising Sun, added a page on PZS Triangle. Also converted some notes from May 8 to eText background/placeholder pages, The Proton-Proton Cycle, and The Carbon Cycle.
October 20-21: Added captions and links to Pictures of Pluto and The Discovery of Pluto, and deleted some outdated images. Also, added more pictures and captions, and moved files from Pictures of Mercury to The Caloris Basin.
October 19: Continued to work on additions and enhancements to Pictures of Mercury, and added a preliminary page on The Caloris Basin.
October 11: Added an animated gif to Pictures of Pluto, to show how a blink comparator was used to discover the planet (text explaining the process to be added later). Also posted the discovery images to the placeholder, The Discovery of Pluto.
October 7: Posted a couple of images from the January and October 2008 flybys of Mercury by the MESSENGER spacecraft. (More images and discussion will be posted once I've finished grading midterms.)
September 29: Posted an answer to a question about the expansion of The Observable Universe.
September 25: Added a discussion of The Earth's Magnetic Field to the page of that name.
September 24: Added (mostly as a placeholder) an image of The Heliosphere, and an illustration and discussion of Plutoids and Plutinos
September 8: Added a brief summary of my views to the "placeholder" on The Moon Illusion.
September 8: Began a major revision of Gravitational Interactions of the Earth and Moon, subdividing it into sections on Barycentric Motion (substantially but not yet completely revised), Tides (merely broken off, and not even close to completion), and Precession (only as a placeholder for now).
September 5: Added a brief discussion of changes in planetary orbital size when the Sun dies, as the start of a page on The Fate of the Earth, and a mathematical derivation of The Effect of Solar Mass Loss on Planetary Orbits, for individuals who would like to see the gory details.
August 17-21: Updated navigation links, banners and titles for every page on the site.
August 3-4: Fixed a number of broken links (mostly but not exclusively due to URL changes at various NASA sites).
July 31: Updated "How Albedo Affects Temperature", in the page on Enceladus, to reflect relatively new information about Phoebe.
July 29: Finished the animation of The Rotation of the Sun.
July 27: Considerably shortened and simplified Nightfall.
July 21: Added two pictures of Saturn's Moon, Atlas. Also, added thumbnails and revised captions to The Moons of Uranus.
July 19: Added an animation to, and expanded the discussion of, The Rosette Nebula.
July 18-19: Added an animation of the Sun's rotation (currently based on eighteen drawings by Galileo Galilei, but to be added to as time allows) to The Rotation of the Sun.
July 13: Added a diagram showing the proton-proton cycle to the still not quite ready to be posted to the eText The proton-proton and carbon cycles.
July 9: Added a caption to the diagram of Jupiter's atmospheric structure, in Atmospheric Structure Notes. Also added and revised a number of terms in the Glossary.
July 6: Added a discussion of The Changing Motion of the Sun, and the variable lengths of the seasons.
June 7: Began adding navigation sidebars with links to other pages of interest. For now, these will only be added to pages which are new, revised, or frequently visited (see Pictures of Neptune, Rotation Period and Day Length, or Pictures of the Moon), but over a period of time, such sidebars should be added to almost every page.
May 27: Added/enlarged/enhanced various Pictures of Saturn, expanded captions and comments for most of them, and added links to source materials for previously uncredited images. Also added The Structure of Saturn, which briefly discusses the structure of the atmosphere, and of the planet itself.
May 26: Posted early images from the Phoenix Polar Landing Site.
May 5: Posted notes from a lecture on The proton-proton and carbon cycles to the site, but did not yet add them to the eText.
April 8: In response to a question about the Venera lander images, added a caption to the Venera 14 images, and a brief discussion to the start of the page.
April 4: Added several images of iron meteorites to Meteorites and Meteor Craters, and began a discussion of meteorite dynamics, and types. Also, later in the day, added a long discussion of Comets, comparable to the lecture I normally give on that topic, to the page formerly called Pictures of Comets.
April 1: Added a brief discussion of the (lack of) gravitational effect of Black Holes at large distances, and posted an additional multi-false-color image of M82 at M81 and M82: A Cosmic Train Wreck.
March 20: Added a cseligman.com Toolbar, with drop-down menus for every page in the eText, and many other onsite/external links, as a navigation tool.
March 16: Added some images and captions to the page on Pictures of Venus.
February 16: Added some material to the page on Lunar Eclipses.
January 27: Further revised Rotation Period and Day Length, to separate the discussion of the Moon's motion from that of the planets.
January 22: Added a note to the table at the end of Rotation Period and Day Length, explaining an apparent discrepancy in the table values.
January 7 - 12: In anticipation of the February 20 total eclipse of the Moon, began to update the pages on Eclipses in general, and Lunar Eclipses in particular.

December 27 - January 12: Started to update class-specific pages for the Spring 2008 semester.
December 16-17: Added some discussion of the death of low-mass stars to Stellar Death, and started a discussion of The Late Main Sequence Life of the Sun. Neither page is likely to be "finished" anytime soon, but what little has been added may be of use to students studying essay question 13.
December 8: For the Celestial Navigation Project, discussed how to adjust the right ascension and declination for circumpolar stars observed passing below the Pole. Also, adjusted the Altitude-Azimuth Project tables, to change E/W azimuth to 360 degree azimuth, and to add a note about observing stars out of order.
October 24: Enlarged upon the discussion of the density structure of the atmosphere, in Atmospheric Structure Notes.
October 18: Posted a larger image of the sequence of stellar spectral types, and added a brief discussion of its meaning, to Stellar Properties. Also copied an image of Fraunhofer's map of the solar spectrum, previously only posted in Background Physics: Light and Matter, to the Stellar Properties page, for comparison.
September 24: Posted an answer to a question about the effect of the Moon on earthquakes, as Moonquakes.
September 2: Added Stellar Motions as a summary of that topic, and posted slightly revised versions of Radial Velocity and Proper Motion.
September 1: Added Radial Velocity as a place holder for further discussion, and The Changeable Constellations, a discussion of the changing appearance of constellations over long periods of time.
August 30: Added a caption to the image of water ice frost taken by the Viking 2 lander in 1979. Also split the discussion of Proper Motion from the page on Stellar Properties, and added a discussion of Mira's spectacular ultraviolet "tail".
August 25: Added credit for aerial image of Ries Crater, on Meteor Craters page.
July 24: Added some notes and images from class discussion to the Summary of Stellar Evolution, and From Protostellar Clouds to Protostars. For the former, discussed how different mass stars approach the Main Sequence; for the latter, how the ionization collapse occurs.
July 20: Revised and enlarged the discussion of Barnard's Star, under Stellar Properties; also modified images of the structure of Jupiter and Neptune, in Pictures of Jupiter and The Structure of the Jovian Planets, to reflect the classroom discussion.
July 17: Fixed (hopefully) a bug in the Shockwave Flash Animation of The Rotation of Mercury.
July 13: Moved the lecture notes formerly linked from the Astronomy 1 (Lecture Class and Telecourse) Information page to appropriate places in the Online Astronomy eText.
July 12: Posted the evening's (brief) notes on Asteroids and Meteorites.
July 9: Added brief page on The Structure of the Jovian Planets, and a diagram of the structure of Jupiter.
July 7: Added NASA diagrams of planetary structure to Pictures of Venus and The Structure of the Terrestrial Planets, and a large version of a Mariner 10 composite of Mercury to Pictures of Mercury.
July 6: Simplified the discussion of Rotation Periods and Day Lengths and corrected some typographical and tabular errors. Also added brief notes to placeholders for The Rotation of Mars and The Seasons on Mars, added a diagram of Mercury's structure to Pictures of Mercury, and a page of pictures taken by Venera Landers on Venus.
June 27 - 29: Added some images of The Seasons, as seen from space, and comparisons of the sizes of the Terrestrial planets and Jovian planets to Our Place in Space.
June 25: Added NASA image of possible structure of Pluto.
June 20-(ongoing): Layout revision of the online text as a result of suggestions for improving navigation. Despite changes in its appearance, the content of the site is unaffected by these changes.
June 10-(ongoing): Layout revision for all pages which seem to pose problems for "software for the blind." Despite changes in its appearance, the content of the site is unaffected by these changes.
May 14: Corrected a misleading section title on the Stellar Evolution page.
Apr 23: Added another image of asteroid Itokawa to the Asteroids page.
Apr 6: Renamed the Online Astronomy Text, the Online Astronomy eText, and began a reorganization of the navigational tools for the eText.
Mar 24: Replaced image of the Earth taken by Apollo 17 astronauts with a higher resolution image.
Mar 5: Added another image to The Rings of Saturn.
Mar 4: Added images of Abell 2667 to Clusters of Galaxies.
Feb 25: Substantially updated the last half of Atmospheric Effects on Planetary Surface Temperature, to reflect information not available when the page was originally posted.
Feb 13: Added a link from Orbital Effects on Planetary Weather to a more detailed page on eccentricity effects not yet posted on the Online eText, consisting of several semesters' notes on the topic.
Feb 10: Added a close up image of the volcano Prometheus to a previously posted image of Io.
Feb 6: Made some minor corrections to The Calendar (which remains in need of overhaul).
Feb 3: Added two images (color, and black and white) of the region near Orion to the page on Stars and Constellations.
Jan 23: Added an image of the Milky Way "setting" to the page on the Motion of the Sky.
Jan 21: Added several images of Comet McNaught to the page on comets.
Jan 8: Added image of the Pointers to the page on Stars and Constellations.
Jan 5: Added colorized image and discussion of (probable) methane lakes on Titan, and an image of recently discovered Comet McNaught.
Jan 2: Added brief discussion of The Galilean Satellites of Jupiter, and some discussion and a data table to the page on Ganymede.