This slide set was made possible through the help of numerous people. Kim Malville (University of Colorado at Boulder) was generous beyond the call of duty in providing reprints and preprints of recent and/or hard to find papers, and in providing us photographic and video material, as well as answering our barrage of questions. Michael Zeilik (University of New Mexico in Albuquerque) provided constructive criticism on an early draft of the text, as well as numerous reprints and preprints. Florence Lister also provided useful suggestions. Mrs. Marcia Logsdon kindly granted us permission to make use of some of her husband's beautiful aerial photographs. We also benefited from the computer graphics expertise of Don Middleton and Tim Scheitlin (SCD/NCAR). Finally, PC and ORW wish to thank Chaco Culture Park superintendant Butch Wilson for granting us permission to accompany the 1997 summer solstice monitoring team to the 3-slab site, and Park rangers G.B. Cornucopia and Gary Henson for their pleasant company throughout a most enjoyable day on Fajada butte. Wendy Hawkins transposed pages to DRUPAL in November 2018 and updated some information. The High Altitude Observatory is a division of the National Center for Atmospheric Research, which is sponsored by the National Science Foundation.

Southwest Aerial Map: Map by Tom Bogdan; top right and bottom left photographs by Paul Charbonneau; top left aerial photograph by Paul Logsdon, copyrighted, and used by permission; bottom right photograph courtesy of Kim Malville, Astrophysical and Planetary Sciences department, University of Colorado at Boulder.
The Seasons: Digital imaging by Don Middleton, Scientific Computing Division, NCAR.
Hovenweep Castle: Photograph by Dick White.
Solstice Window, Solar Symbol Petroglyph, Fajada Butte, 3-Slab Slit, Sun Dagger, Cliff Palace, Lunar Astronomy, and Solar Astronomy: Photographs by Paul Charbonneau.
Hopi Tawa Kátsina: Photograph by Curt Zukosky, NCAR.
Solstice Marker: Images digitized from the video The Hovenweep Sun Dagger.
The Sun Temple: Floor plan redrawn from chapter 8 of J. McKim Malville's Prehistoric Astronomy in the Southwest. Slide set produced April 1999. Copyright HAO/NCAR 1999-2004.