On June 29, 2005, the Spanish Principe de Asturias, Felipe de Borbon, visited Calar Alto on the occasion of its 25 year anniversary, and the celebration of the agreement with CSIC to jointly operate the observatory over the next 10 years together with the Max Planck Society. The commemorative act at the telescope floor of the 3.5m dome was assisted by the 'Secretario de Estado de Universidades e Investigacion', Salvador Ordonez, the president of CSIC, Carlos Martinez Alonso, the 'subdelegado del Gobierno en Almeria', Miguel Corpas Ibanez, the managing director of MPIA, Thomas Henning, the director if IAA, Jose Carlos del Toro, and the former president of the Max Planck Society, Hans Zacher. To a surprise to all and in a clear but most welcome violation of the protocol, the Prince addressed the invited guests and the staff in a closing speech, pointing out the commitment of the Spanish Crown to support Science, and his affection to Astronomy. The visit was accompanied by numerous journalists from the local and national media.

The visit was framed by two other events which provided a very strong presence of Calar Alto in the national press and television. During the week of June 6-10, a public astronomy week was held at the Apolo theatre in Almeria with a lectures given on each of the five days. The event culminated in presentations by Nobel Laureates Robert Wilson and Anthony Hewish on their discovery of the cosmic microwave background and the pulsars. The second event, which covered Deep Impact on July 4, 2005, is described below.

The instrumentation available at the Calar Alto telescopes suffered a drawback with the failure of LAICA during the first quarter of 2005. LAICA is presently back at the MPIA in Heidelberg for repair and is scheduled to arrive on Calar Alto again in August. One of its four CCDs as well as an entrance window had to be replaced. The cause of the failure is not known. The repair of the 1.23m telescope proceeds more slowly than anticipated, due to manufacturing problems of peculiar telescope mount which is in progress at a company in Germany.

On the positive side, the remaining instruments perform according to specifications. The technical down time including telescope failures continues to be below 2 percent at the 3.5m telescope. Significant improvements are reported for PMAS, where a sophisticated  data reduction package for integral field spectroscopy has been made available to the user. The package is described in the article by Sanchez & Cardiel below. An optical speckle camera, previously used at the OAN 1.5m telescope, has been successfully used at the 3.5m telescope.

Calar Alto participated in a major international endeavor to observe the effects of the Deep Impact Mission on Comet 9P/Tempel 1. A monitoring programme PIed by Luisa Lara from the IAA started in January 2005. The observations were carried out at the 2.2m telescope and provided regular imaging and spectroscopy during perihelion approach. It led to the determination of  variations in the gas to dust ratio, in the abundance of the major gas-phase cometary molecules such as CN and C₂,  and the development and distribution of active areas on the nucleus. Those observations were the only of their kind obtained before Deep Impact.

Other scientific highlights obtained at Calar Alto include the continued work on the sub-stellar mass function in sigma Orionis (Caballero & Bejar),  the search of post-AGB stars (Miranda & Pereira), the discovery of the ionising star of the North America and Pelican Nebula (Comeron & Pasquali), and giant nebulae around distant radio galaxies (Villar-Martin, Sanchez, & Peletier).