On the last day of November, 1609, Galileo trained a 20x-perspective glass on the moon, and was rewarded with the sight of lunar sunrise over the Janssen walled plain. This was the beginning of his intensive period of telescopic astronomical discovery. The Paduan professor's observing programmes became possible through his refinement of the telescope, the interpretative acuity of his eye and mind, and the acquired proficiency of his hand. Galileo's ability to draw startlingly important conclusions from his observations, and his skill at their broadcast helped mould modern astronomy. Four centuries later his achievements and our ever-changing relationship to them form a principal theme of the International Year of Astronomy. The image of Galileo as a hands-on natural philosopher suggests active involvement in IYA2009, which at its best becomes a spectacle with no passive viewing from the sidelines: a Galileo moment, whatever form it may take, is an act of observing.

In that spirit, the RASC Astrosketchers' Forum is sponsoring a "Galileo Observing Challenge", to encourage any RASC member to enter into active dialogue with any portion of Galileo's early telescopic observing work. This project was developed at the prompting of Barry Matthews, based on a suggestion of Gary Seronik's in the 2008 SkyWatch. The principal is simple, the rules few.

• Do your own hand-drawn image(s) of any of the objects Galileo reported in his Sidereus nuncius (the moon, or Jupiter and its four largest moons [the "Medicean stars"], the Pleiades, the Praesepe (Beehive) cluster, and the objects around the belt, sword and the rest of Orion), use any optical means you like - provided that the combined magnification of your system is between 3x and 30x - like those employed by Galileo, and submit electronic jpegs of your images at 300dpi to [email protected] by September 1, 2009 with the subject heading Galileo Observing Challenge.

• Include a description of the object(s), the optical means used (aperture, focal length,and magnification), and most importantly, what you experienced, learned, or grasped in active dialogue with the first printed telescopic astronomical images. Your reflection could be any length, from a three word sentence to a thousand word mini-essay, whichever seems right to you. You could report on what it is like to try to limit yourself in some way to the instrumental conditions of an early 17th-century observer, or on the experience as a way to approach Galileo as a fellow observer, or on an insight into what Galileo was able to accomplish, or how contemplating his observations allows you to see familiar objects in a different light.
• The image can be in any hand-produced medium; pencil and paper, crayon, chalk, watercolour, charcoal, pen and ink, acrylic, woodcut, engraving, lino-cut, collage, stained glass, etc. You can make the project as simple or as creative as you like. You can use any modern telescope (or binoculars or opera glasses) you already own, or you can use a reconstruction of a Galilean telescope. Likewise, the style and technique of your image can be thoroughly twenty-first century, or you can use the techniques and materials available to Galileo, or anything in between.

All the entries with descriptions will be put on the website after the "Galileo Observing Challenge" closes. A selection from the entries received before June 1 may be used for an exhibition at the 2009 General Assembly August 13-16 at Cypress Hills Interprovincial Park.

Accept the Galileo Observing Challenge, and interact with the rich cultural heritage of astronomical history to explore the present!