The International Occultation Timing Association 24th Annual Meeting at Mt. Cuba Observatory, Greenville, Delaware
September 30-October 1, 2006
Al Webber and Cliff Bader
Tazya Yeelin and Dr. Bruce Thompson discuss results of the 7 Iris occultation
David Dunham and Richard Nugent demonstrate a Pickett slide rule
David Dunham gives an equipment demo
Ed Lurcott and Bruce Thompson
Paul Maley explains results of the September 22, annular eclipse
Paul Maley and Guy Nason
Total lunar occultation video
Paul Maley shows how to economize flights
Greg Lee and Dr. Wayne Warren discussing the 25 Phocaea event
Mt. Cuba Observatory, Greenville, Delaware
Mt. Cuba Observatory, Greenville, Delaware
Highlights of the 24th IOTA Annual Meeting, 2006
Mt. Cuba Observatory, Greenville, Delaware
by Richard Nugent, Executive Secretary
The 24th annual meeting of the International Occultation Timing Association was held Saturday and Sunday September 30-October 1, 2006 at the Mt. Cuba Observatory in Greenville, Delaware. This location was chosen to coincide with the favorable asteroid occultation of 25 Phocaea in the evening of October 3, 2006, the day after the meeting. The meeting location was hosted by Gregory Lee of the Mt. Cuba Observatory/Delaware Astronomical Society.
Persons present at the meeting included:
President Dr. David Dunham from Maryland,
Vice President Paul Maley from Texas
Executive Secretary Richard Nugent from Texas,
Kathy Buczynski, Edwin Lurcott, Chester County Astronomical Society, Pennsylvania
Ken Coles, Geoscience Dept., University of Pennsylvania,
Greg Lee, Mt.Cuba Astronomical Observatory, Delaware Astronomical Society, Delaware,
Dr. Bruce Thompson, Tayza Yeelin, Physics Dept., Ithaca College, New York,
Guy Nason, Royal Astronomical Society of Canada, Ontario, Canada,
Dr. Wayne Warren, Towson University, Maryland,
Al Webber, Pennsylvania
Don Gardner, Maryland,
Michael Chesnes, Maryland,
Cliff Badon, Pennsylvania
John Kmetz, Lehigh Valley Amateur Astronomical Society, Pennsylvania
Saturday, September 30
President David Dunham opened the meeting and began with introductions of attendees. Dunham then began with a primer talk on ‘Basics of Observing Occultations, Lunar Meteors and Eclipses.” This presentation included the various types of high speed celestial events such as total, grazing, planetary and asteroid occultations, the less frequent occultations by comets, planetary satellites, trans-Neptunian objects and lunar meteor impacts. Dunham then described his first graze predictions and attempted observations from the 1950’s. On October 30, 1957, Dunham described the β Cap (m = 3.1 double star) event over the Los Angeles area, showing a map of the southern limit computed with the Occult program. On that night, from his home in La Canada, California, the 15-year-old Dunham saw the star get closer and closer to the Moon, and skim over the mountains above the South Pole, when he saw the m = 6.0 component disappear, but not the m = 3.1 primary. An occultation had been predicted for the “standard station” in central California, but no prediction for the Arizona station. During this occultation, he realized that he was a short distance on the wrong (south) side of the southern limit of the occultation, and that if he had been a little farther north, at the limit, the star would disappear and reappear among those southern lunar mountains. Dunham thought that it would be neat if someone would calculate those lines, so that one could travel to them to observe grazes, but at the time he didn’t think he would ever be able to do that.
But the situation changed after Dunham took a course in solid geometry at the University of California at Berkeley. For the March 12, 1962 Aldebaran graze, Dunham was armed with sine/cosine, log tables along with a Frieden calculator. He found that the path was to go just south of the San Jose area. He had a 2.4 inch telescope but not a car. He finally located a ride that Sunday evening. While being driven, he was watching the star get closer to the Moon. He saw and timed the reappearance at Palo Alto, but missed timing the disappearance - he saw it from the car while crossing the Dumbarton Bridge. Time had run out on the last Aldebaran graze in the U.S.A. during that Saros (actually, Meton, the sidereal equivalent) 18.6-year cycle. But Dunham was close enough to the southern limit to see the star reappear “like a drop coming slowly out of a faucet” and realized that, with the near-grazing geometry, he had seen a gradual reappearance caused by the large angular diameter of the orange giant star.
Several other notable events in the field of the modern occultations era were:
1962 September - Leonard Kalish first person to travel to witness a predicted graze near
Castic Junction, California
1962 – Dunham wrote his 1st Fortran program for predicting grazes
1963 March 31, Dunham’s 1st graze observation near Rosenville, CA with Bruce Bowman
1975 – IOTA formed
1977 June 5 - a repeat of the β Cap graze (18.6 year Meton-saros cycle; the graze series lasts a few years so it was almost 20 years sicne the October 1957 observation) near Ashton,
Virginia with 12 observers
1983 – IOTA incorporated as a non-profit corporation by Vice President Paul Maley
Dunham then showed a video he made the previous night before the meeting, he recorded 5 total occultations with a Celestron-8 and the Supercircuits PC-164C camera.
Dunham described the many scientific uses of occultations including early determinations of longitude, mapping the lunar limb profile, refining the lunar orbit (pre-laser ranging), use of the limb profile to study Baily’s Beads to measure possible solar radius variations from eclipses, identifying areas for lunar polar ice deposits, discovery of new double stars and measuring stellar angular diameters.
Dunham showed the lunar limb profile determined from the Delta Sco graze of July 27, 1985 from Wellton, Arizona. It showed the duplicity of Delta Sco (0.25² separation) plotted by G. Rattley with 9 stations. Eighteen years later on December 21, 2003, this graze was repeated and Dunham obtained video from two stations (the first ever remote station for a grazing event), and Wayne Warren made a visual observation under clear, crisp, sub-freezing conditions at Rockaway Beach, New York City.
Dunham continued the presentation by describing the various methods used to record and time occultation events:
Visual, eye and ear
Visual with tape recorder
Video – transportable by car
Video – airplane transportable (Richard Nugent’s system)
High speed photoelectric system (usually only found at major observatories)
CCD drift scan (the star trails across the CCD chip with the clock drive off)
Remote unattended video sites
Cameras/systems recommended from long term IOTA experience are:
Supercircuits PC-164C – low light 0.0003 lux C-mount camera, 1/3² CCD chip
Supercircuits PC-23C – 0.04 lux camera with built in microphone (bright star
occultation events only)
Watec 902H – low light 0.0003 lux C-mount camera, with larger 1/2² CCD chip
f3.3 focal reducer – makes for a larger field of view and squeezes the starlight onto
fewer pixels making them brighter.
Other occultation/eclipse milestones included:
1961 – first asteroid occultation event seen in India involving 2 Pallas
1970’s – more solid observing program and predictions,
1974 – Hal Povenmire’s 0.7 sec occultation by a possible satellite of 129 Antigone,
October 12, 1974
1977 – Paul Maley’s 0.5 second occultation of a possible satellite of 6 Hebe
on March 4-5, 1977. This is the first event recognized as a possible natural satellite phenonmenon involving 3.6-mag Gamma Ceti A.
Both of the main occultation paths crossed well south of Povenmire and Maley in Mexico/Central America, thus it appears that the observations were likely the result of a small satellite of each asteroid.
1983 – May 29, 2 Pallas occultation over TX, FL, LA, AZ, Baja – 130 chords obtained
1991 Jan 19 – 216 Kleopatra occultation reveals the unusual cigar shape
Ed Lurcott was in attendance at this meeting and he was one of the observers on this famous Kleopatra event, an account which was published in the January 1992 issue of Sky and Telescope magazine.
1997 – CCD astrometry - having the asteroid and star on the same CCD chip
1997 – release of the Hipparcos catalogue giving high precision star positions
Wayne Warren mentioned that the Hipparcos reference frame is now 16 years old and its precision is deteriorating with each passing year due to the unavoidable propagation of errors. At the current time, only the Europeans have plans to launch a new astrometry satellite and this is several years away. The following other notable asteroidal occultations were described:
2003 Mar 23 – 704 Intermania was observed by Hawaii and Japanese observers
2003 Jul 18 – 1263 Varsavia was observed by 43 observers on the US west coast
2005 Oct 19 – Regulus occultation by 166 Rhodope over Europe
2014 Mar 20 – Next Regulus occultation by 163 Erigone over northeast US
Although not a specific IOTA activity, Dunham talked about the 1999 Leonid lunar meteor impacts caught on video with other observers including Brian Cudnick who made the first confirmed visual observation of such an event from Columbus Texas. Dunham himself used a 5² telescope and PC-23C camera and videotaped the dark side of the Moon. If it were not for Cudnick’s visual observation, Dunham may have never noticed the 3 frames in which the impact occurred.
2001 Nov 18 - Laurel Maryland a spectacular meteor impact was confirmed by
Tony Cook at Arlington, VA and Roger Venable at Augusta, GA.
Baily’s Beads has been the subject of much research over the last 3 decades to measure possible solar radius variations. Richard Nugent’s well known mosaic of video frames covering 30 seconds from the February 26, 1998 total eclipse over Curacao showed this effect.
Dunham then moved on to a complete equipment demonstration of his 5-inch telescope, Supercircuits PC-164C video, Collins image intensifier and KIWI video time inserter.
In regard to power supply issues, Guy Nason suggested taping power adapters connectors to the device cords to avoid having sub-freezing conditions cause metal contacts to expand/contract and come loose (disconnected).
Following the equipment demo, Executive Secretary Richard Nugent gave a status report on the IOTA Observer’s Manual. Nugent is the Editor in chief of the project and he showed sample pages of the nearly 400 page manual which includes 12 chapters, 15 appendices and over 120 figures and diagrams, many in color. Several publishers were contacted and sent all of the chapters. The receptive ones include Willmann-Bell, Inc., Richmond, VA, and Oxford University Press, Cambridge, England. Perry Remaklus of Willmann-Bell estimated it would 2-3 years to get to the shelves with his usual time scale for editing, finishing figures/diagrams, etc. Remaklus runs a 1–person company hence his time is limited as he spreads it out over several books in the works. Cambridge University Press astronomy division is looking at the manuscript and will report back to Nugent in 1-2 months as to their decision. Both publishers are concerned that this book represents a specialized area of amateur astronomy and the major issue is how many copies it will likely sell.
With a potential long publish time another option Nugent proposed is to make the book available online. This could be done immediately and updated as new methods/techniques are developed. IOTA could even make an e-book and charge a fee for downloads. The discussion remained open and Nugent will stay in touch with the Officers and offer proposals as publishers get back with him.
The meeting ended at 6:30 PM and the attendee’s went out for dinner to continue the discussions.
Business Meeting, Sunday, October 1, 9:50 AM
After a brief wrap up of Saturday’s meeting for newer attendees, Wayne Warren motioned the floor to open the business meeting. Secretary/Treasurer Art Lucas was unable to attend this year's meeting and the financial report was read by Dunham through an email Lucas had sent the Officers. Summary of balances are:
Starting Balance: Sep 28, 2005 $ 7,318.93
Ending Balance: Sep 16, 2006 6,504.91
Net Decrease in Bank Balance: ($814.02)
Total Income $2,700.00
Printing Costs $1,325.73
Web Service $ 137.00
Mailing costs $1,019.55
Fees and interest $ 59.43
Cost sharing for IOA/ES grazing
occultation observation data entry
and New Zealand Occultation Section
reimbursement $ 970.00
Total Costs $3,518.07
The cause for the $814 loss was due to the one time grazing occultation observation data entry and the New Zealand reimbursement. Other wise IOTA’s balances are as they have been for the past several years – relatively unchanged. Vice President Paul Maley suggested that large expenses like this $814 be brought to the attention of the Officers in the future to avoid any unexpected impact on the bank balances. Maley also asked how the publication costs were broken down. Dunham said it’s between US and foreign postage.
Dunham moved to accept the financial report, Nugent seconded it. There was no opposition to the financial report, and it was accepted by the members. An original copy of the Annual Financial Statement is on file with the Executive Secretary.
Art Lucas has asked the members at the 2005 meeting to seriously consider taking over his job as Secretary/Treasurer due to his age/health reasons. The main duties of the Treasurer are:
1. Mail the ON from the printer,
2. Deposit member dues checks into the bank,
3. Make a year end financial statement (2 pages),
4. Maintain a membership list,
5. Prepare lists for distribution, i.e., the annual planetary occultation predictions for North America.
From email communication, Chad Ellington has volunteered to do the job. Chad, who has recently moved to Washington State, was in the process of taking over the Secretary/Treasurer’s duties from Lucas. This came at the right time, since the 2007 Sky and Telescope Occultation article needed an address for a point of contact for interested observers.
2007 is an election year and all current Officers present agreed to continue (Dunham, Maley and Nugent). There is an opening for Vice-President for Grazing Occultation services. This position requires graze predictions be sent out to observers upon request.
Dunham suggested that a new yearly award be started within the IOTA organization. The proposed annual Homer F. Daboll award would be given to an IOTA member that has made substantial contributions to occultation science. Homer F. Daboll was the first editor of Occultation Newsletter. Daboll was a major graze observer/leader in the Chicago area and was the person who coined the term ‘IOTA’ as the International Occultation Timing Association. Possible recipients of this award were discussed by the attendees and Guy Nason agreed to set up the mechanics for producing the award. Guy has much experience with awards and the process thru the RASC.
Paul Maley mentioned the nagging problem of funding for IOTA activities. IOTA has a backlog of unreduced observations (especially solar eclipse Baily’s beads tapes). This eclipse activity represents a constant travel cost for IOTA members. Several sources of funding were discussed including Museums and other Benefactors. Wayne Warren mentioned that NASA seems to have continuous funding (mostly grants) for undergraduates. But these are hard to come by and here are the usual long delays, strings attached and politics to deal with. Other possible funding sources mentioned by attendees were the USRA and the Keck Foundation. The Keck foundation is widely known for its generosity to the field of astronomy, an example is the large telescopes on Mauna Kea in Hawaii named the Keck telescopes.
With no further business, at 11:00 AM the business portion of the meeting was closed.
David Dunham continued the meeting with a status report on IOTA’s long-term effort in solar radius experiment and research. Dunham had presented the results of his research at the 2005 SORCE (SOlar Radiation and Climate Experiment, a NASA satellite launched in 2003) Science Meeting September 14-15, in Durango, Colorado. A 3-year grant proposal was submitted in April 2003 and accepted in December 2003, and finally funded by NASA in June 2004. The principal investigator is David Dunham, with co-investigators: Wayne Warren, Jr., Alan Fiala, Harry Bates, Sabatino Sofia, David Herald, Patricia Rosenzweig and help from many IOTA observers. The main focus of the research was to analyze Baily’s Beads timing data from solar eclipses to search for solar radius variations. Previous eclipse data analyzed and published in 1994 included eight eclipses from 1715 to 1987 giving small changes of the solar radius relative to the 959.63² standard value for each of the eclipses.
Videos of Baily’s Beads obtained during the eclipses of 1991, 1994, 1995, 1998, 1999 and 2002 were analyzed in part with David Herald’s Baily’s Bead module of the program OCCULT. James Thompson, a NASA summer mentor student, performed most of the work under Dunham’s supervision. The results indicate solar radius changes varying from 0.06"± 0.06" (Aug 11, 1999 eclipse) to -0.27"± 0.02" (May 1994 eclipse). A plot of the solar radius changes didn’t show any obvious trend, however this doesn’t prove that there isn’t a cycle of small scale solar radius changes occurring with the Sun.
In the past 12 months, results of the eclipses of October 2005 and March 2006 were added to the research as well as the May 20, 1966 eclipse and a few others. Dunham was discussing the January 24, 1925 solar eclipse over the northeast and how it was used to compare the solar radius when Al Webber had said that he had seen and photographed that eclipse !! He was living in the northeast and used a 5 x 7 camera to photograph it. Al’s 99th birthday was just nine days away on October 10, thus Al was 18 at the time of the 1925 eclipse.
One of the major issues in this research is the criticism of the lack of standardization of equipment used for the Baily’s Bead’s videos. Different telescope systems and different solar filters were used at each of the eclipses studied and this may be partly responsible for the inconsistent results. Different filters allow different maximum wavelength transmissions of the Sun’s light to be analyzed possibly affecting the Bead timings. Dunham suggested that Richard Nugent’s compact 4-inch telescope system with Thousand Oaks solar filter would be useful to use as a standard system.
It was suggested testing all equipment and combinations side by side at the next solar eclipse. The videos/bead timings can be analyzed for any type of variation or systematic errors.
The meeting continued with the discussion of the asteroid 144 Vibilia. It has occulted several stars in the recent past months and some results were discussed.
August 21, 2006 Guy Nason observed a chord from Ontario and that event produced three occultations and one miss, the other observers were Geoff Gaherty, Ken Kingston and Tom Lubin.
August 14, 2006 – Washington State, British Columbia and Alberta, observers Walt Morgan, Mike Hoskinson, Guy Mackie.
September 15, 2006 – 5 chords were obtained. Dunham had a miss.
September 19, 2006 – Eric Frappa published the results of Vibilia occulting the double star TYC 1879:2151 (COU 5814) with a separation of 0.25². Detailed results are on his web site www.euraster.net.
12:30PM Lunch Break
Bruce Thompson and Tayza Yeelin presented their results of the occultation of 16 Piscium by the “S” class asteroid 7 Iris that occurred on May 5, 2006. They showed their equipment setup which included time insertion video. They did a photometric analysis of the event using Mathlab. Thompson gave a discussion of the pixel analysis and how he determined the position angle and distance of this previously unresolved (directly) close binary star. Their results suggest a separation of 10 mas (milli-arc seconds) and a position angle range of 59° – 79°. 16 Psc was not previously confirmed as a double star, however this observation gives credible evidence to indicate it is. Thompson and Yeelin submitted a paper on their results to the journal Publication of the Astronomical Society of the Pacific (PASP).
Dunham proceeded to discuss the method of using remote video stations to time occultations. Since occultation predictions are now accurate to ±10 seconds, using a focal reducer with say a ¼ ° field allows a wide field of view for pre-pointing a telescope. The method involves choosing a star with the same declination as the target star, pre-point the non-motor driven telescope to this star, and at occultation time the target star should drift into the field of view while the video is recording. The choice of a pre-point star depends on how long before the occultation you pre-point. If you pre-point 1 hour before the event, the target star would have to have a right ascension that is one hour (-10 seconds for the sidereal time) less than that of that of the occultation star. This method adds additional complexities into the occultation process. If you use a camcorder and set up 1 hour before occultation time, you’ll need a battery that can last for an hour and enough tape to run for 1 hour while your’re off to another station. And then there is the problem of jammed tapes, running out of tape, battery failure, an animal rubbing up against the tripod causing it to move (such as a cat or even deer), etc. Roger Venable solves the problem with battery power by using camcorders that have pre-programmed start times. He programs the unit to turn on say 10 minutes before the occultation. Venable also spray paints his equipment flat black to make it more invisible to intruders and usually positions them 100 feet off the side of roads. Roger Venable and David Dunham are the most successful remote station observers in the occultation business.
The first ever remote station that timed an asteroid occultation was that of the September 7, 2001 9 Metis event in northern California. This account was published in Sky and Telescope in the March 2002 issue. Seven additional events have been timed by Dunham since then (several other times, he remote station recorded an occultation, but the attended station failed or had no occultation). Dunham’s record to date is three successful stations for any one event. Not to be outdone by Dunham, Venable setup and had 4 stations time the 2 Pallas event on June 12, 2006. Not only is this a record, but the magnitude drop was only 0.15!
Paul Maley presented preliminary results of the September 22, 2006 annular eclipse he observed in Kourou, French Guiana. This was Maley’s Ring of Fire Expedition #33. This eclipse was the first one to pass over the Devil's Islands group since the total eclipse of December 22, 1889. Plans are under way for the August 1, 2008 total eclipse over China including IOTA’s recording of Baily’s Beads at the umbral limits. The price at this time is $2,999 (land only). This high price is due to the fact that the eclipse is 2 weeks before the summer Olympics in Beijing.
Maley continued the discussion with his continued search for asteroidal moons. It has been 29 years since he made the March 1997 0.5 sec observation of a possible satellite of the asteroid 6 Hebe from Texas. His results: From 1972-September 2006 – 1384 attempts, most of them since 2003 with 58 successful occultation observations. Some of the challenges in pursuing asteroid occultations are:
a) last minute airfare decisions,
b) airline regulations on carry-on (equipment),
c) WWV time signal reception (this problem can be solved by using GPS time
d) road travel time/cost
e) faint stars (now regularly 11-12th magnitude)
f) Police encounters
g) Arriving at the site too late due to unavoidable delays beyond control
For 2006, Maley has not seen any suspected satellite events, and all his successful occultations had instantaneous D and R events.
Maley had also traveled to Taiwan to observe the occultation of the m = 6.7 star HIP 33643 by 372 Palma on September 1, 2006. Unfortunately this event was clouded out. Paul’s contact in Taiwan was Dr. Wen-Ping Chen of Lulin Observatory. This observatory is not accessible by conventional roads as we are used to in the United States. To get to the remote Lulin Observatory first you drive, then you hike to the summit.
Maley concluded with a presentation entitled, “IOTA: Defining New Worlds”. Although this presentation is designed for audiences unfamiliar with occultations, it could also be used for seeking funding from various sources. The main goals described were the observation of solar system bodies, the basics tools needed, the science of determining the true shapes of asteroids, satellites and the discovery of double stars.
Richard Nugent then presented a series of occultation animations using Microsoft’s Power Point features. These animations illustrated how asteroid shadows move across the Earth, close ups of asteroids passing in front of stars, plus grazing occultation animations. Nugent uses these animations in talks he gives to astronomy clubs and other groups to illustrate the nature of how occultations and eclipses work. This allows IOTA astronomers to determine the sizes and shapes of asteroids, the Sun and to determine the lunar limb profile during grazes. Nugent passed out CD’s of the animation talk to all attendees to assist in their presentations.
Dunham showed maps for the remaining good grazes in 2006 for North America and Europe and the 2007 grazes for North America. He said that starting in 2007, Sky and telescope will no longer have space allocated to show graze maps for Europe, only for North America. Highlights include a Regulus graze by the 34% Moon in June 2007, and a graze of a 5th magnitude star during the March 2007 total lunar eclipse.
Asteroid events for 2006:
755 Quintilla October 18, m = 7.6 star HIP 4176A & B. Canada/USA, Mexico. This
is a double star (ADS 732) with a separation of 0.2². The B component, m = 8.8
ground path is parallel and approximately 100 miles north of the primary’s ground
1403 Idelsonia November 8, m = 8.5 star. South Carolina. Very low altitude event.
70 Panopaea December 14, m = 8.6 star. Baja to southern Georgia.
372 Palma, January 26, m = 6.2 star 32 Lyncis, Northern California to Delaware
Pluto, March 18, m = 14.0 star, across North America
72 Ferona, March 28, m = 7.5 star, Baja Mexico to Cuba
411 Xanthe, April 18, m = 4.2 star, northern Florida
146 Lucina, September 20, m = 7.9 star, California to Michigan
219 Thusnelda, December 18, m = 6.7 star, Mexico to South Florida
With these events, the meeting adjourned around 6:30 PM and the attendees made station plans for the 25 Phocaea asteroid event the following night.
Post meeting: The Phocaea event was observed at 16 stations and a very interesting chord was obtained by Brad Timerson who was on the western path limit. He video recorded what appeared to be a double dip in brightness of the eastern tip of Phocaea. This could mean a high mountain feature, a possible asteroid satellite or a double asteroid nature for Phocaea, but in this case it was almost certainly a high mountain.
IOTA's Annual Meetings
The International Occultation Timing Association is the primary scientific organization that predicts, observes and analyses lunar and asteroid occultations and solar eclipses. IOTA astronomers have organized teams of observers worldwide to travel to observe grazing occultations of stars by the Moon, eclipses of stars by asteroids and solar eclipses since 1962.