Terry's Occultation Page
Greeting from West Palm Beach
This month's page will contain three items. First is a report of an observed occultation by Hans Heynau and me. Second is a short essay on why we should do occultations and other amateur astronomy activities. The third item will be my normal pick of the best occultation to do here in the Palm Beaches and or south east Florida.
Observation ReportHans Heynau and I observed (2612) Kathryn occult 6.4 magnitude star HIP 34608 April 25, 2013 at 8:22 PM from Redding South Observatory (RSO). Hans came over early and setup on the grass about five meters east of the observatory. He used a 50mm Mighty-Mini occultation scope. I had the normal array of instruments available at RSO. These included the 14" SCT, an 80mm refractor and a 70mm refractor. This was a bright star occultation which would normally be viewed easily with any of the four instruments at our disposal. However, two factors made this a somewhat more difficult event to observe.
First, the event time. At 8:22 PM the sun would be at -8 degrees west and the sky would not be fully dark. This primarily meant that finding the target star would be problematic. We solved this problem by star hopping from Sirius, which could be viewed in binoculars beginning at 7:50 PM to dimmer stars as they emerged. We were both on the target star about fifteen minutes before the event.
Second, the duration of the event. This event was scheduled to last no longer than 1 second. Hans was setup to record WWV during the video recording of the event. This approach is doable with a 1 second event. But just barely. We added an IOTA-VTI GPS to Hans' video recording path. The device time stamps each frame to the millionth of a second making it possible to detect very short events of as little as 0.133 seconds in duration. However, if the asteroid held true to the predicted path Hans might see a drop in star light in as many as 30 frames.
Here is Hans' light curve:
There is something very cool about actually seeing a star disappear as the asteroid blocks it's light and then reappear after the asteroid has passed. In order to help observers stay focused and attend to observing it is helpful for one member of the group to count down the seconds to the event as we watched for the star to disappear. We did this, but noted only the slightest flicker at the event time. Later as Hans analyzed his video record of the event using Tangra he noted the classic slight dip in light and then drop and recovery and then exit shoulder. The duration of his event appears to be the minimum, four frames. We are now looking hard at the other video recordings to see if we can confirm the event. Currently Hans has an unsure report. Additional stations north or south of us could have easily confirmed this event. We need more observers. Next I would like to share with you a short essay on why we should do scientific occultation observations.
Science.So why do science? Why do occultations? Why look at double stars? Why indeed. Because our very lives may depend upon it.
My best occultation pick for May/June 2013.
There are several excellent occultations scheduled to occur in May and June. Maybe the most exciting is the May 8th event when Pluto occults RIO 184740.9-194142, a star of undetermined magnitude. Sadly it will be too faint for most of us to observe. Indeed, the planet at magnitude 14.1 will most likely be more visible than the star predicted to be at between 9.1 and 16.4 magnitude. The wide variance in the predicted star magnitude indicates there is an error in the forecast.
During the month of June there are two favorable occultations. I have selected the brighter of the two, when (694) Ekard occults 10.6 magnitude star TYC 5605-01058-1 on June 5th, at 02:43:55. This event should last up to 10.5 seconds and may be seen with telescopes of 4" aperture or larger.
The image below shows the list of future occutations for our area. Please note the event I have highlighted an event scheduled to occur June 5th, 2013. There are no better events between now and then that I would recommend to the south east Florida amateur astronomers.
The image below shows the predicted path of the asteroids shadow. Observers from Orlando to Miami should consider observing this event.
Don't forget to try for a high precision time. Tape record WWV at 10 or 15 MHz while visually announcing the D dissapearance and the R return of the star.
For those with an interest in chasing shadows there is an entire community of amateur and professional astronomers that daily coordinate worldwide to observe and report on occultations. The International Occultation and Timing Association (IOTA), where you can learn more about them, can be found here: http://www.occultations.org/.
Two resources readily available to those in the Palm Beaches are the web pages maintained here: http://www.poyntsource.com/New/Regions/Redding.htm, and here: http://www.hristopavlov.net/OccultWatcher/OccultWatcher.html.
The first is a website updated each month by Derek Briet for amateur astronomers in the Palm Beaches. He lists future asteroid and lunar events. His web products are created with Occult v4.
The second website is the home of Occult Watcher. This program is the one I use to create a list of potential occultations and mutual events that can be observed from my location, or near my location. It is a very easy to use program that has become essential for those wishing to chase shadows and coordinate their efforts with the larger community of observers.
Lunar Grazes information can be found here, http://www.timerson.net/IOTA/. The page contains a path map for each event predicted to occur in the next 45 days. Each Graze event also has a link to detailed information about the star and the time of the event. Tools designed to aide you in plotting the best observation site through a Google Map inspection are also provided.
If you have an interest in occultations, and would like help getting started, please feel free to contact me.
Now lets chase some shadows.
Terry - W6LMJ - 14.287
Terrence R. Redding, Ph.D.
Redding Observatory South, West Palm Beach, Florida
How do amateur astronomers learn?
This research supported by Redding College of Palm Beach
American Association of Variable Star
Observers (AAVSO): RTN http://www.aavso.org/