-------------------------------------- Proposal: Hodierna Deep Sky Tours An Urban/Suburban program for IYA 2009 -------------------------------------- Hello, everyone. As the International Year of Astronomy 2009 approaches, I'd like to propose a special kind of urban and suburban observing program that will invite people to experience the thrill and challenge of deep sky observing with binoculars and explore the contributions of a great 17th-century astronomer: Giovanni Battista Hodierna (1597-1660). ---------------------------------- 1. About Hodierna: Some background ---------------------------------- While astronomers such as Galileo and Kepler focused mainly on the nature of our Solar System, Hodierna in Sicily took a special interest in nebulae: "cloudy" objects in the more remote stellar realm which might give clues as to what William Herschel would later term "the construction of the heavens." Like his more familiar colleagues in this opening era of telescopic astronomy, Hodierna relied on the revolutionary and yet in retrospect quite modest optics available to him. He mentions using a refractor with a magnification of 20X. In 1654, he published a breathtaking catalogue of deep sky objects, many of which are also featured in Messier, NGC, and other later catalogues, and still treasured by avid observers as among the premier attractions even in bright urban or suburban skies. The Hodierna Deep Sky Tours project would offer community-based presentations and star parties introducing people to these objects and to the joys of deep sky observing, while taking advantage of two intriguing connections between Hodierna's 17th-century tools and techniques and ours in early 21st-century Sacramento and environs. First, while (as far as I know) Hodierna does not specify the aperture of his telescope, something like 60mm seems to have been about the practical state of the art around 1654. His sketches and star maps, according to one modern analysis, suggest a limiting magnitude of 8 or so -- comparable to the situation in Sacramento with 15X70 binoculars. Although Hodernia didn't face modern urban light pollution, he did have to contend with the quite imperfect state of optics before 1750 for revealing low surface brightness objects such as most external galaxies. Thus many of the items in his catalogue and star maps hold up surprisingly well under today's city skyglow. Secondly, Hodierna during his mature years did his observing from Palma di Montechiaro in Sicily, at a latitude of about 37.2 degrees north -- quite comparable to Sacramento at around 38.5 degrees. As he noted, this location permitted him to "observe and admire... some stars that are of southern declination" and could not be seen from the more northerly precincts of Europe. In or around Sacramento, likewise, we can marvel at Hodierna's southern wonders such as the open clusters NGC 2451 and NGC 6231, notably absent from the famous later catalogue of Charles Messier, who observed from Paris. One of Hodierna's projects, invaluable even in its unfinished state, was a star atlas in 100 maps, of which a few pages in manuscript have come down to us. He was evidently interested in marking the locations of nebulae as well as stars, and the available maps give clues as to deep sky objects not detailed in his published catalogue of 1654 which he evidently observed. -------------------------------------------- 2. Hodierna Deep Sky Tours: Some first ideas -------------------------------------------- Hodierna's known and suspected deep sky discoveries and rediscoveries (the identity of some objects is a topic for lively discussions) are all visible in the Sacramento area, and most of them to good effect with 15X70 binoculars. Such binoculars, when placed on a parallelogram mount, allow for friendly and flexible group viewing as well as opportunities for people to try their hand at starhopping and sweeping from one object to another with an accommodating 4.3-degree field of view (much greater than that of a Galilean telescope, one might add!). The idea of the Hodierna Deep Sky Tours would be to combine a bit of historical background and orientation with lots of hands-on deep sky viewing. A special focus would be on urban or suburban venues offering a measure of protection from direct light trespass and glare, so that participants can focus in a reasonably undistracted way on the joys of observing, and learn in a friendly environment about dark adaptation and star party etiquette. Various public and private places might serve as venues, and arranging the best available locations may be an educational process all around as to the varieties of light pollution confronted in our SVAS area. One format might combine the orientation and observing sessions into a single event, with an hour of orientation and questions followed by two or three hours of observing, scheduled so as to accommodate the season. In a school setting, a presentation as part of a science or history course might serve as preparation for an observing field trip either that same evening or on another day -- possibly a weekend when family participation might be maximized. If the school is fortunate enough to have at least part of its grounds reasonably sheltered from direct light trespass, then the whole process could take place onsite. Otherwise, an observing field trip or community event in the same neighborhood or area could serve the same purpose. Well presented, the Hodierna theme should serve as an open door to the realm of astronomy both in its engaging historical development and current state of understanding, as well as to the fine art of observing and of friendly coexistence at star parties. It's fitting that the name Hodierna is related to the Latin word _hodie_ ("today"), and could be translated as "modern" or "up to date." His suggestion that the arrangement of stars may have a logic not immediately discernible from our terrestrial vantage-point, and his wonder at the vastness of the universe that the hypothesis of a heliocentric Solar System, coupled with the observed reality of (then) immeasurably small stellar parallaxes, would imply, makes him indeed a pioneer and premier explorer of deep space. Also, a focus on Hodierna's objects should by no means be taken to exclude the enjoyment of others. In the summer, for example, while observing NGC 6231 (known in more southerly latitudes as the "Northern Jewel Box"), M6, M7, and NGC 6530 (the open cluster of M8), we would find it natural to visit the nearby M24, M25, and M22. Likewise, in winter, surveying M41 and M47 would invite a detour to M93. In addition to overlapping with the familiar Messier catalogue and NGC, Hodierna's objects also include two items likely identical to those listed in Collinder's catalogue of open clusters as Cr 135 and Cr 140 in Puppis and Canis Major respectively. -------------------------------- 3. Modes of outreach and inreach -------------------------------- While public presentations in amenable urban or suburban venues have a special potential for attracting new astronomers and enriching our agenda for the International Year of Astronomy (IYA) 2009, other means of "virtual" outreach and inreach are also possible. Web pages about the Hodierna objects and urban binocular astronomy, mailing lists or Web-based discussions where people can exchange ideas and observing experiences, and telephone or e-mail mentoring for SVAS members who are seeking help or advice in observing in or around their own homes or apartments may prove equally effective strategies of outreach and inreach. These ideas grow out of my own experiences with urban deep sky observing, and a certain curious realization that two notable "non-Messier objects" in which I have taken special delight, NGC 2451 and NGC 6231, are both among the celestial features of a "southern declination" that Hodierna evidently chronicles in his own catalogue and maps. Needless to say, these objects are equally relevant and yet more beautiful at dark sky sites: my focus on urban and suburban settings is meant to be illustrative rather than exclusive! As the "Sicilian Galileo," or "Galileo of the Deep Sky," Hodierna should attract particular attention during IYA 2009, with its focus on the advent of the telescope and the 17th-century developments that followed. Equipped with often superior optics, but confronted with the modern challenge of light pollution, the urban or suburban binocular observer is aptly situated to make IYA 2009 a saga of living history. Most respectfully, Margo Schulter mschulter@calweb.com 20 December 2008