December 2010 Meeting Notes
Discussion of business items this month included a request for ideas and volunteers for 2011 meeting programs, a quick review of the preliminary 2011 observing schedule and an assessment of our current publicity channels and how we can broaden our visibility within the local community. After the business meeting, Steve Plank gave a demonstration of his new, back-saving observing chair. This month's program, titled "Observing Asteroid Occultations", was presented by John Grismore.
Observing Chair Demonstration - Steve Plank
Many of us have experienced stiff, achey or fatigued back muscles after too many hours bent over a telescope eyepiece while observing. But those problems are a thing of the past for Steve Plank. He's found a perfect solution in the StarBound Deluxe Quick Adjust Observers Chair. This is a sturdy, well built, yet portable chair that can adjust the padded seat height from 9" to 32" with a simple lift and slide motion. It provides back support and stable, tip resistant lateral support. Despite its ability to support over 300 pounds, this chair can fold into a compact profile for portability. Steve's experience with the chair so far has already convinced him that it's well worth the money. We can expect to see him sitting comfortably at all our future observing activities. For more information about the StarBound Observers Chair, visit the following link:
Observing Asteroid Occultations - John Grismore
Astronomy is one of the few areas of science where amateurs can make significant contributions, and asteroid occultation observations are an especially good example. With nearly 500,000 "known" asteroids in the solar system, drifting slowly in their orbits across a background of 14,000,000 stars visible to a typical 8" amateur telescope, its not surprising that asteroids eclipse stars fairly frequently. In his presentation, John discussed the geometry of asteroid occultations, what they look like, how amateurs observe them and the value of occultation data gathered by amateurs.
Aside from the science, observing asteroid occultations can be a rather surprising, even startling, experience. In most cases, the asteroid is too faint to be seen, so its approach to the target star is undetected, until suddenly the star winks out and is gone for many seconds, then just as abruptly reappears. Observing such an event for naked eye stars can be as simple as watching with the unaided eye, while occultations of fainter stars will require binoculars or a telescope. And all that's required to capture scientific data is to record the time the star disappeared and the time it reappeared. Those two numbers, submitted to the International Occultation Timing Association (IOTA), are all that's needed to contribute to a better understanding of the asteroid's orbit, shape and size.
While timing an occultation can be as simple as using a stop watch or a WWV radio, in recent years many occultation observers have moved to the Video/GPS method, which provides unprecedented accuracy. In this method, a relatively inexpensive, but very sensitive video surveillance camera replaces the eyepiece in the telescope, and its video signal is routed through a GPS video time insertion box, which timestamps each video frame with Universal Time, received from GPS satellites with an accuracy of 1 millisecond. This timestamped video is recorded to tape or directly to a laptop disc, for later analysis to determine the precise disappearance and reappearance times of the target star. Knowing the observer's latitude and longitude, these two times define precisely where the asteroid was (between the observer and the star) during the occultation.
The real value of amateur observations of asteroid occultations comes when there are multiple, geographically separate observations across the width of the shadow path. Correlating and aligning these observations can result in determination of the size, and the shape profile of the asteroid.
Amateur astronomers are particularly well suited to provide useful occultation data to professionals. There are many, many amateurs distributed around the world, capable of making such observations, providing the advantage of far more coverage than professional astronomers and observatories could ever hope to do. In addition, the rapid advances in inexpensive, but sophisticated equipment and software, have given amateurs the leverage to contribute observations and data at a level that could only have been achieved by professionals just a few years ago. Not only do these observations provide information about main belt asteroids, but ongoing developments are quickly bringing to amateurs the ability to also make important contributions in the area of Earth approaching asteroids. The expanded monitoring that's possible with many amateurs making such observations could be an important addition, if and when an near Earth asteroid appears with our name on it.
Monday, January 3, Rick Bryant will present "The Cheapskate Astronomer’s Introduction to Astrophotography", in the Bartlesville Public Library Meeting Room. For more information, see the meeting announcement on our website home page at <http://sites.google.com/site/bartlesvilleastronomyclub/> .
BAS Public Website: http://sites.google.com/site/bartlesvilleastronomyclub/
BAS Yahoo Group: http://tech.groups.yahoo.com/group/BvilleAstro/
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