The International Occultation Timing Association 26th Annual Meeting at Lewis Center for Educational Research
Apple Valley, California
September 12-14, 2008
Standing left to right: Scotty Degenhardt, Sandy Bumgarner, Gene Lucas, Earl Wilson, Chuck Herold, David Dunham (holding plaque), Derek Breit, Greg Lyzenga, Mark Vincent, Danny Falla, Mike Collins, Kerry Coughlin. Sitting left to right: Roc Fleischman, Richard Nolthenius, Steve Preston, Richard Nugent, Walt Morgan, Karen Young.
Bob Buckheim's presentation of the Homer F. Daboll award
Lewis Center for Educational Research
David Dunham opens the meeting
Mark Vincent, Bob Buckheim (at telescope), Danny Falla
Scotty Degenhardt's "Might Mini" telescope system
Scotty Degenhardt showing his multi-station deployment technique
Walt Morgan talks about GPS datums
"80 mm Shorty" telescope system
Walt Morgan conducting the video sensitivity test
Lewis Center Observatory
Nearby Mt. Wilson 100" telescope. Edwin Hubble's chair is at lower left
Highlights of the 26th IOTA Annual Meeting
Lewis Center for Educational Research, Apple Valley, California
September 12-14, 2008
The 26th annual meeting of the International Occultation Timing Association was held Friday-Sunday September 12-14, 2008 at the Lewis Center for Educational Research in Apple Valley, California. The Lewis Center was the site of IOTA’s 23rd annual meeting in 2004. This location was chosen to coincide with the occultations by 9 Metis, 153 Hilda, and 58 Concordia. The Metis event was the most favorable event for North America in 2008 and occurred at approximately 11:22 PM PDT on September 11th (6:22 UT Sep 12th). Numerous positive chords were obtained and the results are posted at:
The Concordia event occurred the next night September 13 at approximately 4:44AM PDT 10:44 UT). A link to the current reduced data on the event can be found at:
No attendees at the meeting had any positive chords for the 153 Hilda event.
The meeting location was kindly hosted by Lewis Research Observatory Director Dave Meyer. The final meeting schedule, and most of the presentation files, are located at Brad Timerson’s North American Observations web site: http://www.asteroidoccultation.com/observations/NA/2007Meeting/
A total of 40 persons participated in the meeting:
At the Lewis Center:
President Dr. David Dunham from Maryland, Executive Secretary Richard Nugent from Texas,
Richard Bean, Derek Breit, Sandy Bumgarner, Bob Buckheim, Danny Falla, Greg Lysenga, Richard Nolthenius, Walt Morgan, Hank Sielski, Mark Vincent, Earl Wilson, Gary Witt and Karen Young from California,
Terry Redding from Florida,
Scotty Degenhardt from Tennessee,
Steve Preston from Washington,
Chuck Herold from Texas
Kerry Coughlin and Roc Fleishman from Baja California Sur, Mexico
Michael Collins, Gene Lucas from Arizona
Video Internet Conference Attendees:
Bob Anderson, OR
Tony George, OR
John Grismore, OK
Steve Messner, MN
Dave Gault, Australia
Gerhard Dangl, Austria
Brad Timerson, New York
Dave Herald, Australia
Dave Gault, Australia
Ken Coles, PA
Randy Peterson, AZ
Jan Manek, Czech Republic
Chad Ellington, WA (IOTA Secretary/Treasurer)
Luis Martinez, AZ
Steve Conrad, MD
Bob Sandy, MO
Pawel Maksym, Poland
Lewis Research Center Observatory Director Dave Meyer welcomed the attendees. President David Dunham opened the meeting and mentioned a few anniversaries: September 11 was the 20th anniversary of the flyby of Comet Halley by the European probe Giotto, September 8, 2008 was the 45th anniversary of the 1st successful 4 station grazing occultation expedition near Davis, CA (at that graze, Dunham had 3 ‘D’s and 3 ‘R’s) and September 7, 2001 was the first remote station video of the asteroid occultation by 9 Metis at Ormand, CA. Dunham then asked the attendees to introduce themselves.
This year’s presentation of the annual Homer F. Daboll Award was made by the Award Committee Chair Bob Buckheim. The Homer Daboll award is given annually to an individual in recognition of significant contributions to Occultation Science. “Occultation Science” is limited to actual IOTA research: total and grazing occultations, asteroid occultations and solar eclipses.
Homer F. DaBoll had a long history with IOTA until his death on March 10, 1990. DaBoll was born on May 22, 1920. He led numerous grazing occultation expeditions in the Chicago area spanning 3 decades, from the 1960’s to 1990. He was the first ever editor of Occultation Newsletter for 16 years from its first issue in 1974 thru early 1990 when health reasons forced him to pass on the Editorial duties to Joan Dunham. DaBoll was the person who came up with the acronym IOTA, International Occultation Timing Association. Members of IOTA have always held Homer DaBoll in the highest regard for his numerous contributions to occultation observations, expeditions, ON, and his many other volunteer efforts.
This year’s committee members included Committee Chair Bob Buckheim from California, Dave Gault, Dave Herald from Australia, Colin Haig from Canada, and Terrence Redding from Florida. The Committee nominated eight individuals to be considered for the award. The Committee’s main objective in selecting an award recipient was to reach a consensus and not choosing someone by a majority vote. The rules allow any person to be considered for the award except for current IOTA Officers and Committee members.
The 2008 Homer F. Daboll award recipient was Edwin Goffin from Hoboken, Belgium for his dedicated contributions since the 1980’s in predicting asteroid occultations and the yearly asteroid occultation supplement. Goffin was previously honored by having an asteroid named after him, 1722 Goffin for his extensive computations in minor planet orbits. Dunham attempted to call Goffin on his cell phone at the time of the announcement but could not reach him.
Buckheim’s proposed a schedule for future nominations of the Daboll award:
8 weeks before the IOTA annual meeting: call for nominations
5 " " " " " " : close nominations
Next 2-3 weeks: Deliberations
Next 2-3 weeks: Ordering the award plaque weeks plus time to have it delivered to the person who will attend the IOTA meeting and present the award.
A discussion was started on the growing concern of the lack of new younger persons entering the field of occultation science and astronomy in general. To be active and involved in occultations does require one to be able to travel and to have portable equipment. Dunham suggested building a special fund to allow financially strapped or younger persons to travel to a major occultation or solar eclipse event. Few observations in astronomy rival the excitement of witnessing a grazing occultation, asteroid occultation or solar eclipse. If a financially deprived person can travel to observe an event alongside an experienced occultation observer, this could spark an interest in astronomy and may lead to a career in astronomy/occultation science. Most IOTA members can recall how they got started in occultations and how they just happen to be at the right place at the right time.
Secretary/Treasurer Chad Ellington reported IOTA’s financial position has remained relatively stable in the previous year. Bank balances are as follows:
Starting balance 2007 Jul 13: $6,621.30
Ending balance 2008 Aug 19: $6,648.48
Net Increase: $ 27.18
The expenses remained low for the past 12 months due to just a single mailing of Occultation Newsletter (ON) and the 2008 Asteroid Supplement. A brief discussion among the attendees resulted in changes to IOTA’s dues structure to deal with high postage/printing costs. Gene Lucas motioned to raise membership dues for those requesting paper mailings of ON and the asteroid supplements to $40/year. Dunham seconded the Motion. The Motion passed. On-line IOTA memberships will remain at $15/year. As always, donations to IOTA are appreciated and always tax deductible as IOTA is a Texas non-profit 501c corporation.
Executive Secretary Richard Nugent updated the status of the IOTA Observer’s Handbook. The completed manual was placed on the internet in early April, 2007 It’s a free PDF format e-book entitled: “Chasing The Shadow: The IOTA Occultation Observer’s Manual, The Complete Guide to Observing Lunar, Grazing, and Asteroid Occultations”. The manual is located at: http://www.poyntsource.com/IOTAmanual/index.htm. The webpage has had over 15,817 hits since being placed on line. The first week the book hit the website, Dr. W. C Yue of the Hong Kong Astronomical Society wrote Nugent requesting permission to translate the manual into Chinese. Nugent happily agreed.
The book has 389 pages, has over 120 figures and diagrams (many in color), an extensive set of references and web resources, a 220 word glossary, a comprehensive set of appendices covering many aspects of occultation work, report forms, equipment setup figures and instructions, shortwave time signal information, IOTA and IOTA-ES annual meeting announcements, tips from IOTA observers and a detailed index.
The main updates to the manual immediately planned will be the new reporting method for total and grazing occultations, since the International Lunar Occultation Center (ILOC) will be closing in March 2009. The popular KIWI GPS time inserter will replace the McAfee time inserter in Chapter 8 (Don McAfee no longer manufactures GPS VTI units).
The on-line book has the advantage that it can be updated easily from time to time as new methods and techniques are developed. It also allows the world to see IOTA’s long celebrated history and numerous original contributions to occultation science. Currently no version #’s are listed on the IOTA Manual download website as changes are made to the manual. Nugent will market the new lunar occultation reporting changes on the website when the updates are completed.
The proposed location for the 2009 IOTA meeting was discussed. The likely location will be the Clay Center in Brookline, MA near the end of August 2009.
With no further business at 3 PM, Richard Nugent moved to close the business meeting. A short break was taken.
Technical Session, Friday Afternoon
The occultation of a m = 6.0 star by the asteroid 9 Metis was observed by several attendees the night before and results were shared. Nine stations had already reported to Brad Timerson’s website by the meeting start. Observers with remote stations included Dunham with 3 stations and 3 hits, and Scotty Degenhardt with 11 stations and 11 misses! Some observers had problems with low clouds on the eastern horizon. Even though the occulted star, HIP 14764 was a relatively bright m = 6.0 star, its low altitude in California (17°) and thin clouds made it a difficult observation for some.
Other observers included:
Kerry Coughlin/Roc Fleischman: obtaining video with a 10" Meade SCT,
Steve Preston: clouded out
Richard Nolthenius: clouds,
Derek Breit with a 50mm camera lens video,
Walt Morgan: two stations, one with a KIWI VTI and one with WWV
Richard Nugent: positive event on video with WWV
Earl Wilson and Gene Lucas: 40.5 second occultation
Following a short break, Walt Morgan presented a talk, “Datum Conversion for KIWI-OSD Displayed Elevations”. The KIWI/Garmin GPS generated elevations have several sources of error, namely sampling errors and geoid height estimation errors. The Garmin G18 LSV outputs coordinates and elevations from two different datums, and most users don't know this. In the field of geodesy, a datum is a reference surface defined by five quantities: the latitude and longitude of an initial point, the azimuth of a line from this point and two constants necessary to define the reference spheroid.
Walt has designed an Excel worksheet for adjusting elevations. The two elevations displayed by the KIWI/Garmin are the WGS84 ellipsoid and the Mean Sea Level (MSL) Geoid. The MSL datum is the basis for the USGS TOPO maps. The situation for KIWI users is that latitude and longitude coordinates are displayed in the WGS84 datum and elevations are shown in the MSL datum.
Walt suggested incorporating a datum conversion worksheet into the reporting software which takes into account corrections to the geoid height displayed by the KIWI unit. The new lunar occultation reporting format on Brad Timerson’s website does have a choice of datums used when reporting coordinates and elevations. Currently for asteroid occultations only a single datum is offered on the report form for both coordinates and elevations. Dave Herald mentioned that some Japanese GPS units return geoid heights. Most hand held GPS units give data using the WGS84 datum and a choice of datums is available by these units. The Garmin G18 LVS unit returns elevations with respect to the MSL. It was pointed out that users should know what datum their unit provides.
Brad Timerson described the new lunar occultation report form that was initiated September 1, 2008. IOTA will be assuming the role as depository for lunar occultation observations for North America from the International Lunar Occultation Center which is scheduled to close in March 2009. This new Excel format form was beta tested for the Regulus graze in October 2007. The new form has drop down menus for certain data fields. Timerson was very careful to include separate datums for the input of latitude/longitude coordinates and elevations (called “height” in the new form). The new form has mandatory data fields marked in green and optional data fields marked in yellow. A red triangle (▼) in the upper right corner of a cell will provide explanation for that cell. John Talbot has created macros for one-click conversion of the data into Occult readable format.
The new form is supported by Occult4 in a separate module for reporting of observations. The Lunar Occultation Workbench (LOW), authored by Eric Limburg is being updated for the new reporting format. All things considered the new Excel form is far more user friendly for reporting observations than the old 76-column email format. As part of the agreement on the use of this new form, only email submissions will be accepted for observation reports, paper forms will not be accepted any longer.
The new form allows for the sending of observations to regional coordinators. In the USA, Derek Breit has agreed to collect observation reports, convert them to Occult4 format and forward them to Dave Herald. The new lunar occultation report form can be downloaded from Brad Timerson’s North American Observations website as a stand alone Excel file.
Dave Herald discussed the new lunar occultation report form and the archiving of occultation observations. He briefly talked about the history of occultation observations and their reporting.
Up until September 1, 2008 the International Lunar Occultation Centre (ILOC) has been the worldwide clearing house organization located in Tokyo, Japan which collects and maintains data from lunar occultation observations from all over the world. Each year the ILOC receives thousands of occultation reports. The ILOC also issues predictions for use in making occultation observations and provides other data for a variety of researchers and research institutions.
The International Lunar Occultation Center was founded by the International Astronomical Union in the United States in 1923 as an organization dedicated to collecting and maintaining occultation observational data from all over the world. ILOC was later entrusted to the Royal Greenwich Observatory before being moved again in 1981 to the Japanese Hydrographical Office, which by then had established itself as a leader in performing occultation observations. In 1992, the work of providing predictions of lunar occultations was taken over from the US Naval Observatory by the same organization.
At one point in the history of occultation observations, graze data prior to 1981 was not available in machine readable format. It was the European observers that were able to extract it and convert it into digital format by reading microfiche and using optical character recognition (OCR) software and all the problems that went with it. Herald stressed that the long term archiving of occultation observations should not depend on any one person due to the risk involved. Toward this goal Herald has convinced the Astronomical Data Center in Strasbourg, France that own/operate the SIMBAD database (Set of Identifications Measurements and Bibliography of Astronomical Data) to accept occultation observations in their standard archiving format. The SIMBAD astronomical database is freely accessible online database that provides basic data, cross-identifications, bibliography and measurements for astronomical objects. It can be accessed by http://simbad.u-strasbg.fr/simbad/. It is similar to the USA based Astronomical Data Center (ADC) which archives just about every astronomical catalog, atlas and survey ever published.
SIMBAD has six internet mirror sites worldwide creating redundancy, stability of the data and easy internet access. This is important so that future astronomers and investigators have access to occultation and other astronomical data.
Dunham mentioned that we would need probably 5-6 regional coordinators for North America alone. Herald disagreed and though the job could be handled by 2-3 people. Terrance Redding suggested using astronomy clubs to assist in the coordinating. Dunham quickly pointed out that IOTA’s local coordinators can get with the local astronomy clubs if needed. The involvement of astronomy clubs into the picture does have the potential of bringing in new observers.
Sandy Bumgarner described a new digital photomutiplier tube that is capable of extracting occultation timings on the order of several microseconds (1 µ sec = 0.000001 sec). The estimated sensitivity of this device could bring the limiting magnitude of a Celestron-8 to approximately m = 12. Collection of the data could go directly into a computer through a USB or stored into a USB flash drive.
The session ended with the planning for the 58 Concordia asteroid event occurring early the next morning. The attendees went to dinner and informal discussions continued.
Saturday September 13, 11:15 AM, Technical Sessions continued
Tony George described the latest release of the program OCCULAR 3.14 (Occultation LiMovie Analysis Routine) co-authored with Bob Anderson.
New features include:
-Comprehensive manual including a quick start guide
-magnitude drop used to test the validity of an event
-magnitude drop and limiting (lim) magnitude calculation added
-lim drop defined as the limiting magnitude of the detector
-Noise histogram of data provided for each event to check quality
-Automatic field or frame sensing routine. This feature checks time step to the field or frame rate
-Events detected are now color coded
-Final report generated for validating potential events
-A random noise based Monte-Carlo analysis will test the confidence level
-Signal to noise ratio (SNR) event detector nomograph provided
Tony demonstrated the new features from past occultation events. The program will show users the various confidence levels:
Above 90% - very confident event, green coded
50%-90% - caution in accepting these as real events, yellow coded
less than 50% - Occular does not recognize these as real events
The final report screen summarizes the noise statistics, confidence level of events, displays the ‘D’ and ‘R’ times plus their estimated errors. Occular is valuable tool for analyzing LiMovie video’s and can identify occultation events that would other wise go undetected. It can be downloaded from Brad Timerson’s occultation website:
The meeting continued with an open discussion about the results of the previous night’s 58 Concordia event. From attendee’s results, a south shift had occurred. Dunham and Scotty Degenhardt described their remote stations and the usual problems associated in setting them up. Dunham had help from Terry Redding and Steve Preston operating stations. While rushing to his 3rd station Dunham had some difficulty locating the target star (the m = +11.3 target star was just 25 degrees from a 96% Moon) and finally found it 8 minutes after the occultation. Five attendees had positive events. With his arsenal of Mighty Minis Scotty Degenhardt added five more misses to his record. These misses (and the 11 Metis misses from the previous night) while not providing chords, they did prove that this series of remote stations can and do video record the target star.
Mark Vincent suggested using a digital inclinometer to accelerate the pointing of telescope systems for remote stations. This would require the observer setting up the station to use the horizon system of coordinates to aim the telescope: altitude and azimuth.
– Lunch Break –
Technical Session continues
Walt Morgan proposed on the IOTA listserver prior to the meeting that the attendees conduct a controlled test of the video sensitivity of the available video cameras/recording systems. The object of this test is to learn how different components in our astro-video recording systems compare while observing the same target. The test was done in the Lewis Center parking lot on Saturday night September 13 and the target used was the open cluster M11 (NGC 6705). The test included 20-30 second video clips of M11 using the PC-164C, PC-164C-EX and the Watec 902H cameras. Walt used 8" SCT and 10" SCT telescopes, plus some smaller scopes for the tests including Scotty Degenhardt's remote station telescope setup. Each camera/telescope combination would be identified by volunteers keeping records. Morgan will use LiMovie for the analysis which he hopes to have results by the end of October, 2008. Internet conference attendee Gerhard Dangl expressed interest to see the results for a meeting in Europe in October.
Richard Nugent gave a presentation on testing one’s video camera’s synchronization with a GPS Video Time Inserter. As proposed in the KIWI instruction manual, the user’s video camera can be pointed at the flashing light (flashing at once/second) on the unit to test the synchronization of the camera. By playing back the video, once can see if the VTI’s seconds display readout on your camcorder’s reaches 0.0000 at the moment the light flashes. Both the KIWI and McAfee GPS time inserters have these flashing lights which are driven by the 1 pulse per second (1 pps) signal from the Garmin GPS 18 LVS unit.
In the test Nugent pointed his PC-164C video camera at his McAfee unit’s flashing light and recorded for 15 seconds. Near the top of each second he examined the video frame by frame and displayed the results. The test showed that when the VTI’s seconds display read 0.0000, the light flashed. The light was not visible on the previous or next frame indicating the length of the flash was less than 0.033 second. Thus in this test, the camera was in synchronization to 0.0001 seconds with the McAfee VTI unit.
Next Nugent presented a comparison study of GPS Timing vs. WWV Timing. In this test he made three 4 minute McAfee GPS time inserted videos. He then sent the videos to Rick Frankenberger who time inserted these with WWV using the Manly time inserter. The Manly time inserter works by listening to the 1000 Hz 800 millisecond tone broadcast at the top of each minute (at the 2.5, 5, 10, 15 and 20 MHz shortwave bands). This tone triggers a crystal quartz clock in the Manly time inserter that begins a running display on the video in the hours/minutes/seconds format. Nugent compared the two and found that the difference between the two timing methods differed in the range of 0.025 sec – 0.008 sec. These differences were calculated by subtracting the actual display time off the videos and correcting for the travel time of the WWV signal to the radio receiver, signal recognition by the Manly unit and processing time to send the information to the on-screen display of the camcorder (both WWV and GPS units). These results show very good consistent agreement between the two different methods of time inserting the videos. In a separate test communicated to Nugent by Frankenberger the day before the meeting, Frankenberger found a 0.066 second error in the Manly crystal oscillator over a 4-hour time period. This works out to just 0.0013 sec error for 5 minutes. The standard source used to compare the crystal oscillator was the WWV signals. Frankenberger notes that this result changes depending upon the time of day and the time of the year, these changes are due to the continuing changes in the Earth’s upper atmosphere.
Nugent then presented the preliminary results of IOTA’s expedition to the August 1, 2008 Total Solar Eclipse in China. This expedition was done in support of IOTA’s continuing study to measure solar radius variations. Nugent and Chuck Herold traveled with Paul Maley’s group to Hami, China and set up their equipment near the south umbral eclipse limit. Herold was set up 3.4 km inside the south limit with a Celestron 5" SCT and Nugent was set up 1.4 km inside the south limit with a 3.5" Questar. In doing this, the duration of the Baily’s Beads effect is maximized as compared to the center line. The observation of the Baily’s Beads from both the north and south eclipse limits allows the determination of the precise width of the Moon’s shadow on Earth. The analysis of the Baily’s Beads on the videos is made by comparing the predicted time of a particular bead’s disappearance/ reappearance to the observed time. The Occult program has a Baily’s Bead module for doing this. These calculations depend critically on an accurate lunar limb profile which has been obtained from 4 decades of grazing occultation observations.
For this eclipse, IOTA-ES had observers had several stations located at both the north and south eclipse limits in conjunction with Nugent and Herold’s south limit stations. Both Nugent and Herold obtained Baily’s Beads videos under clear steady skies. Nugent showed his 2 minute video which showed the Beads clearly. At his location, he had about 16 seconds of totality and Herold had approximately 24 seconds of totality 2 km further north.
In past eclipse analysis, the time extraction of a Bead’s disappearance/reappearance was dependent upon an observer watching a video who estimated them to 0.10 second. Unlike star occultations, this is a very difficult observation since the ‘D’s and ‘R’s are not instantaneous, rather the Beads tends to slowly fade in/out and merge with other Beads as the eclipse progresses. Nugent had picked several Beads both just before 2nd contact and just after 3rd contact to demonstrate a new technique in measuring Bead timings. He used LiMovie’s 3-dimensional contour plots in a frame by frame analysis to watch when the light level of a particular Bead disappeared. When the contour peak dropped to zero intensity, it’s a simple matter to read off the display the GPS VTI inserted time. Nugent showed that this could be done quite rapidly and accurate times to 0.033 sec could be obtained for Bead events. This new method should prove quite useful in the reductions to arrive at a solar radius. A webpage with Nugent’s Baily’s Bead video and observation summary is located at:
Scotty Degnhardt presented his “Unattended Prepointed Multistation Deployment Technique”. Inspired by Paul Maley, Scotty has developed a unique, small easily deployable series of small telescopes for multistation recording of asteroid occultation events. After experimenting with various combinations of equipment, he has developed the following system:
1. Orion 80mm spotting scope (nicknamed the “80mm shorty”). This telescope system can reach stars to m = 11 with the PC-164 EX-2 camera
2. Mighty Mini – a small 60mm finder scope capable of reaching m = 9 stars. It uses the PC-164 EX-2 video camera and an OWL focal reducer. Its FOV is 2.4° x 3.2°.
3. Both systems use the Canon ZR-10 camcorder which allows for direct digital A/V input recording.
Scotty’s next goal is to come with an Orion 10" SkyQuest telescope/video system capable of reaching m = 14. The Field of view would be about 23' x 31'. Scotty estimates the practical observing magnitude limit with the PC-164 EX-2 camera and Mogg focal reducer would be about m =13.8.
Ideally when preparing for a multistation setup, a straight stretch of road is preferred. Interstate access, good shoulders, free of obstruction, and low population are all considerations when deciding to do an event. When setting up a station, Scotty time stamps the video with a KIWI VTI. For each site he loads the lat/long in Garmin’s MapSource software and uploads it to his hand help GPS unit. Since he started keeping records on his multistation deployments, his setup times have decreased thus he gets faster and faster deployments. This allows ultimately for more stations to be deployed. Scotty says the learning process gets faster and faster with each station he deploys for a given event. By the time he gets to the 6th station (the 6-pack), his deployment time is down to around 10-12 minutes.
Even though Scotty had a total of 16 misses for the two events 9 Metis and 58 Concordia, he gained tremendous experience from the deployment process. His next major event will be on September 26, 2008 when 216 Kleopatra will occult a star over Northwestern Canada. For this event Scotty plans to setup 20 stations !!
In his developing of the multistation technique, Scotty has coined two methods of deployment: Stamp and Run and Deploy and Run.
Stamp and Run. In the stamp and run process, Scotty sets up all the stations first without turning on the video. He then returns to each station where he turns on the video and time stamps it with the KIWI VTI. By using a video cable Y-splitter, he can connect the KIWI unit, do the time stamp and disconnect it without disturbing the running camcorder. The Stamp and Run method allows many stations to be setup.
Deploy and Run. In the deploy and run process, stations are setup and turned on one at a time. This allows fewer stations to be deployed compared to the Stamp and Run method.
In analyzing occultation videos from the Cannon ZR-10 camcorder, Scotty found that this unit adds two fames per minute. This apparently is a built in correction by Canon to account for drift and frame skips. By KIWI time stamping the Canon at the beginning of a long 60-minute test run, he can determine the frame rate errors and correct for them. All in all, Scotty Degenhardt has revolutionized the unattended video station technique. His multistation technique may be the method that allows IOTA to discover and map more asteroid moons as well as add large numbers of chords to expected low observer turnout events.
Steve Preston presented his study entitled “Review of Path Prediction Statistics”. The Primary goal of this study is to assign an accuracy estimate for each asteroid astrometry measurement from an asteroid occultation. He used over 800 previous events which have yielded profiles for asteroid relative to the occulted star.
The accuracy of an observation which results in a profile is a function of the number of observers, distribution of observers, and quality of the data. The accuracy of the astrometric position for asteroid is a function of the accuracy of the observation and the accuracy of the star position. Ultimately, the accuracy of an astrometric position derived from an asteroid occultation is largely dependent on the star position’s accuracy. Preston’s secondary goal in this study was to ascertain the accuracy of the generated uncertainty in path predictions.
Preston notes that currently, we do not have access to a methodology for assessing the accuracy of our asteroid occultation observations via direct measurement. Thus we cannot directly examine the accuracy of either the predicted uncertainties or the observational error. Preston reviewed the statistics of the overall 800+ occultation event dataset and searched for inconsistencies.
Preston’s asteroid occultation predictions consists of two quantities that asteroid observers require: 1) the estimate of the time of the event and 2) the estimate of the path of the event.
Following his analysis of the events he determined that the actual standard deviations of the path predictions were on the order of 125% higher than the predicted ones from the original path errors quoted on his website. The standard deviations of the time of central event were on the order of 163% larger than his predicted times. It is clear that no prediction is perfect including its estimate of uncertainty. But overall, the IOTA community has recognized Preston’s predictions and estimates of the uncertainties in the path predictions in the highest regard and they are clearly the best available. Only in rare cases of asteroids with highly accurately known orbits (such as orbital data obtained with the NEAR mission to 433 Eros) can the times and path predictions be made with extremely high precision.
The meeting was adjourned around 6 PM and the attendees went to a local restaurant.
Saturday evening in the Lewis Center parking lot – Walt Morgan and the attendees performed the video sensitivity test using several telescopes and video camera combinations on the open cluster M11 (NGC 6705). The sky conditions were clear with relatively steady dry air.
Sunday September 14 at 9:00 AM – Technical Sessions continued
Scotty Degenhardt started the Sunday morning session with the talk “What is DDRA?” This is his Dirt Digger Running Average (DDRA) method of reducing occultation videos. DDRA can be used:
1) When unable to lock on a target object in LiMovie, DDRA creates a new AVI with a higher S/N.
2) When your time stamp is unreadable DDRA can provide a means of pulling the numbers out of the noise.
3) When all else fails to succeed in reducing your RAW AVI.
Scotty devised DDRA by having it create a running average by averaging individual fields, not just frames, thereby providing twice the data. For instance a 3 frame running average will use 6 fields to average together, a 6 frame running average uses 12 fields, etc. It is possible with DDRA to create a 1 frame running average by simply taking the two fields of the same frame and averaging them together.
By utilizing individual fields, and not just frames, Scotty is able to two-fold increase the dataset available for LiMovie analysis. Scotty explained the method of creating a new AVI file with the fields for LiMovie to analyze. He showed the results of applying the technique to a previous event 892 Seeligeria on July 12, 2008. This event had a signal to noise ratio of just 0.75. Using the DDRA process and Occular 3.10, a 2.60 ± 0.042 second occultation was detected, which would otherwise have certainly gone unnoticed by a routine visual analysis of the video.
As part of his experiment, Scotty purposely increased LiMovie’s circular measurement aperture to reduce the SNR and thus increase the noise level. Using apertures of 5,6,7,8,9,10, 11 and 15 pixels, this corresponded to SNR’s of 1.17, 1.11, 1.01, 0.89, 0.81, 0.75, 0.69 and 0.59. After running DDRA and Occular 3.10, the event times were still extracted with 0.033 second accuracy. DDRA and Occular are powerful tools in the analysis of high noise occultation videos.
David Dunham showed maps of some remaining favorable grazes and asteroid events for the remainder of 2008 plus favorable events for 2009. With reduced space that Sky and Telescope normally provides Dunham for his yearly Lunar Grazing Occultation Highlights (published since 1968) he now places most of the graze maps and data at http://iota.jhuapl.edu/grazemap.htm. These asteroid events are listed on Steve Preston' and Derek Breit's websites.
For 2008, bright star remaining asteroid events:
Sep 16, 2008: 14424 Laval occults an m = 4.3 star, Oregon to Mississippi.
Sep 18, 2008: 205 Martha occults an m = 6.6 star. Northwest Territories to southeast of Hawaii.
Sep 26, 2008: 216 Kleopatra occults an m = 7.7 star over Northwest Canada to Australia. With Kleopatra’s known 5-hour rotation rate, there would be a 30°- 40° change in viewing angle from Canada compared to Australia.
Oct 11, 2008: 64 Angelina occults an m = 9.2 star. Southern Mexico/Florida, Russia, United Kingdom, Scandinavia.
Nov 16, 2008: 583 Klotilde occults an m = 9.6 star. Eastern Canada to Eastern USA.
Nov 19, 2008: Venus occults an m = 8.1 star over the SE USA.
Nov 23, 2008: 98 Ianthe, m = 8.4 star. Path over New England. This is a low altitude event over the extreme NE USA. Roger Venable’s 2004 video of Ianthe showed a possible moon.
Remaining 2008 Grazes:
Several Pleiades passages will occur in 2008 and 2009.
Oct 7, 2008: V Sag. Path is East coast USA with a 46% Moon.
Oct 6, 2008: φ Sag., m = 3.2, very favorable with a cusp angle 16°. Graze path from New Orleans area to Maine.
Favorable 2009 Asteroid Events:
Feb 17, 2009: 185 Eunike, m = 9.2 star. Washington state to Central Mexico.
Mar 7, 2009: 95 Arethusa, m = 9.6 star. Central Canada to Delaware.
Mar 13, 2009: 217 Eudora, m = 10.3 star. Eastern Canada to S. Carolina.
Apr 12, 2009: 3471 Amelin, m = 2.5 star. The star is γ Corvi, a/k/a Gienah. Southern Baja, Central Mexico, Columbia, Venuzuela. The current path uncertainty is 4-sigma for this 30 km sized asteroid.
Oct 20, 2009: 139 Juewa, m = 6.5 star. Greenland to Northwest Canada.
Nov 16, 2009: 344 Desiderata, m = 11.0 star. Central California to S. Carolina.
Dec 6, 2009: 423 Diotima, m = 10.9 star. Southern California to Florida.
Dec 24, 2009: 216 Kleopatra, m = 10.7 star. Baja to Central Canada.
Dec 25, 2009: 81 Terpsichore, m = 8.5 star. Central California to Central/NE Canada.
Several favorable Pleiades grazes occur in 2009. Observers can refer to the 2009 Observer’s Handbook for path maps and details.
The Antares graze is the most favorable for 2009. It occurs on Feb 17, 2009 over Western Australia with a 46% Moon about 60° above the eastern horizon. Dave Herald’s daughter lives near the path about a day’s drive northeast of Perth; he is making plans for it since weather prospects away from the coast are good; very hot summer temperatures are expected. The current series of Antares grazes ends in 2010 and doesn’t begin again until 2024.
The proposed 2009 IOTA meeting site is the Clay Center in Brookline, MA (near Boston) scheduled to be hosted by Ron Dantowitz. The date will likely be late August 2009. On August 27, a daytime graze of Antares occurs with a 54% sunlit Moon in the New England area. This will be a low altitude event with the star 19° above the southeastern horizon.
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.