Photometry course for amateurs at Calar Alto

From the 16th to the 18th of October 2009, a course on astronomical photometry for amateur astronomers was given at Calar Alto Observatory. Using the professional facilities of the Observatory, this absolutely new initiative was conducted by Calar Alto specialists with the aim of training amateur astronomers in the basics of astronomical absolute photometry, applied to the standard measurement of the brightness of the night sky. The final goal is to constitute a wide group of people capable of contributing to international campaigns of evaluation and reduction of light pollution in Spain and Europe.

The 1.23 m Zeiss telescope used for the practical lessons in this course.

The first course on astronomical absolute photometry given at Calar Alto Observatory is a total novelty in the Spanish and European astronomical landscape. A group of 16 selected amateur astronomers from many different areas of Spain have had the chance to use the professional Zeiss 1.23 m telescope of Calar Alto Observatory, equipped with a research grade CCD camera and standard photometric filters. From the 16th to the 18th of October 2009, these outstanding enthusiasts have received the practical and theoretical background in the classical astronomical technique of absolute photometry.

All the students were qualified amateur astronomers, selected on the basis of their previous experience, taking into account the telescopes and instruments available to them at their homes and/or associations, and with a demonstrated capability for later spreading their newly got knowledge among their groups, or at public outreach institutions.

The course was oriented towards the final measurement of the brightness of the sky background, with the intention of contributing to international campaigns of evaluation and reduction of light pollution. This group of 16 qualified people should constitute the nucleus from which a wider army of measurers will arise, well spread all over the Spanish geography, to assess the current situation in relation to light pollution in our country. This should be done relying on objective, homologated methods, suitable for being used in international studies, and meaningful for astronomers of any kind.

This initiative is framed in the international "Dark Skies Awareness" cornerstone project, locally powered by the IYA 2009 Spanish Node. The activity has been partially financed by the Spanish Foundation for Science and Technology (FECYT), and has been supported and organised by a series of public and private organisations: Pamplona Planetarium, Calar Alto Observatory (CAHA), Andalusian Network for Technological and Scientific Public Outreach (RECTA), Cel Fosc (Spanish Dark-Sky Association), Complutense University of Madrid (UCM). The intention of the organizing committee is to give continuity to this activity in years to come. The StarLight initiative and the Unesco Programs created to protect and preserve the beauty of the natural landscapes need measurements of the night sky brightness of professional quality. Several international projects are already in developement aiming to an accurate scientific assessment of light pollution. The collaboration with the amateur astronomers is essential to cover the largest possible fraction of the Spanish surface. So, this course, which is born as part of the activities of the International Year of Astronomy 2009, is intended to become an annual initiative in order to spread these photometric techniques among the Spanish community of amateur astronomers. CAHA facilities at Calar Alto Observatory, as was shown in this first edition of the course, offer an ideal location for this initative, what makes Calar Alto an excellent candidate to become the course permanent venue.

The students have got a strong and vivid hands-on experience under dark skies (a zenital brightness of V = 21.20 mag/sqr arcsec was determined during the course) in a professional first-line international observatory. Strong links have been established among a wide network of individuals and associations. This absolutely new collaborative experience between the professional and amateur communities will give fruits during the next months.

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