Embedded Files
Teachers learn how to use digital cameras to unlock views of constellations and more
May 14, 2011
By Richard DeCoster and Margie Corp for Stars at Yerkes News
How can you see a satellite with a digital camera? The answer is found in the science of astrometry. At the final Stars at Yerkes workshop of the year, teachers examined this along with a new view of their constellation photographs previously taken.
The workshop began with a presentation by ARCS teachers Elizabeth Ramseyer and Rich DeCoster, demonstrating how to use the website Astrometry.net (http://www.astrometry.net/) to identify constellation pictures. Contributing Stars at Yerkes scientist Richard Kron had introduced teachers to this program at the AAS meeting in Seattle last January. Since then, Rich and Elizabeth worked to see what great things could be done with the program. Kron added to the discussion by giving some background on the development of the program and some of its features. Our participants readily took to this program and sent about twenty pictures to the service to be identified. Most had amazing success and were quite pleased with their results. Elizabeth Ramseyer and Rich DeCoster work with images using astrometry.net
To briefly summarize: you take an image of the sky with your digital camera. You send your jpeg image to Astrometry.net and usually within seconds, the image is solved and the constellations and stars in your photograph are identified. In addition to the identification, the program returns an assortment of data and image files to the user. Participants spent some time working through some of these items. One such file (new.fits) is a fits format of your original image that can be opened and analyzed with standard astrometry software such as ds9.Astrometry illustrated using a simple constellation photo.
Elizabeth Ramseyer used a Kodak Z1015 camera to obtain images of the sky from her home. She has set up a program at her school, Niles West High School in Skokie, Illinois, for extensive student contributions to our image repository. An observation target, as it reaches a ten-month maximum, is the Mira variable R Leonis. Elizabeth took pictures of Leo with the Z1015 that clearly showed the presence of this star. Professor Kron delivered a wonderful talk on geostationary satellites. He identified some of the interesting aspects of these satellites and discussed the distinction between “geostationary” and “geosynchronous.” He discussed the location of these satellites and showed us where one should aim his or her camera to find one. The images he showed of these satellites were quite amazing. The idea is that the satellites are orbiting with the same period as the 24-hour period of Earth and thus appear to stay in the same spot with respect to an Earth-bound observer. But the stars are truly stationary and thus appear to move with respect to this same observer. Kron’s ~100 second exposure revealed an image rich the streaks that corresponded to the stars and with a series of dots, not streaks, that were the satellites!
Kron discussed numerous features of the image: its distribution of streaked star images, the handful of stationary satellites, and what information could be obtained by analyzing them. One interesting aspect was that even though these satellites follow orbits that suspend them exactly over Earth’s equator, from our location they do not appear among the equatorial stars. Due to the phenomenon of parallax, they appear to like some angular distance below the equator, the exact distance depending on the longitude of the observer. Satellites appear as stars and stars look like streaks in this photo by Rich Kron.Rich Kron was at his best in explaining to us numerous projects, including student projects, that could be developed that utilize aspects of the observation. But the amazing feature of the presentation was the beauty of his image, with the little dots beading along an image otherwise filled with many stellar streaks.
In another session, Yerkes Education and Outreach Director Vivian Hoette described her research on her favorite star, SS Cyg. Vivian talked about this cataclysmic variable, and how she was mentored in its study by Janet Mattei, long-time director of the American Association of Variable Star Observers (AAVSO). Over the past decades, Vivian has taken many images of this star and prepared numerous educational outreach activities based on the analysis of these images. As a long-term goal, Vivian is trying to understand some of the more subtle aspects of the variations that she has recorded for this star, including how the light output from the star varies at different colors or wavelengths. Vivian Hoette discusses variable stars with in-person and virtual participants.
The workshop ended with a session about using the Afterglow feature of the Skynet observing system to make a light curve for a star. Josh Haislip presented this via Skype from North Carolina. With help from ARCS teacher Kevin McCarron and Vivian, Josh walked us though the procedures to make a light curve. This was a follow-up to our April workshop that featured the use of the Skynet system and its light-curve producing capabilities. Josh is continuing to develop additional aspects of the program. It was really cool to see how easy this process was, once the series of files was properly prepared. For practice we created a light curve for a supernova that was caught early on in its explosion, while the object was still getting more luminous. Stars at Yerkes scientist Al Harper joins the group discussion on Skynet and SOFIA.Participants also shared the day both at Yerkes and in remote locations. As the Stars at Yerkes Professional Learning Community grows and explores additional outreach topics, the opportunities for sharing these sessions via telecommunication were tested. We hope our efforts to bring the latest information and innovative teaching strategies to our classrooms and beyond will stimulate student and teacher learning and research projects, as well as enthusiasm for astronomy and the unseen universe. Vivian Hoette and ARCS teacher Kate Meredith assist virtual participants.
Our calendar of workshops for next year will be posted August 2011. Please check with us then for information about more exciting learning opportunities with the teachers and staff of Stars at Yerkes. Happy Summer!
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