The International Occultation Timing Association's 33rd Annual Meeting
University of Southern Nevada Cheyenne Campus
North Las Vegas, Nevada
October 16-18, 2015
by Richard Nugent, Executive Secretary
Gerhard Dangl, 2015 Homer F. Daboll Award Recipient
Bob Sandy - 2015 David E. Laird Award Recipient
The 33rd annual meeting of the International Occultation Timing Association was held Friday, Saturday and Sunday October 16-18, 2015 at the University of Southern Nevada Cheyenne Campus, Las Vegas, Nevada. This location coincided with the occultation of the asteroid 215 Oenone covering a 39-km wide projected path near the meeting site early Saturday morning October 17, 2015.
The meeting location was kindly hosted by Rob Lambert of the Las Vegas Astronomical Society. The final meeting schedule, and most of the presentation files, are located on the IOTA web site presentation page:
The people participating in the meeting in person and via internet conference:
On site attendees: President Steve Preston, Vice President Dr. Roger Venable, Executive Secretary Richard Nugent, Ted Blank, Russ McCormick, Tony George, Bruce Holenstein, Bob Sandy, Dylan Holenstein, Dr. Terry Redding, Stephen Arthur, Ernie Iverson, Walt Morgan, Steve Conard, Paul Maley, Larry Fleming, Danny Falla, Rob Lambert, Bill Hanna, Chuck Herold, Karsten Schindler.
Internet Conference Attendees: Dr. David Dunham, Derek Breit, Art Olsen, Rafael Chavez, Chris Patrick, Brad Timerson, Rob Robinson, Ted Swift, Jan Manek, Gerhard Dangl, John Brooks, John Newman, Chad Ellington, David Herald, Elizabeth Warner. NOTE: If you were an online attendee and your name isn't here contact Richard Nugent, email RNugent@wt.net to be included.
1:00PM – Meeting start – Introductions
Vice President Dr. Roger Venable opened the meeting and welcomed everyone to the meeting.
President Steve Preston thanked Rob Lambert of the Las Vegas Astronomical Society and the University of Nevada for the use of the facility for the meeting. Steve also mentioned that Kerry Coughlin, one of the "Baja Boys", who contributed numerous positive asteroid occultations from Baja California, passed away last year. He will be missed.
Steve Preston then presented Rob Lambert with a Special Achievement Award for his contributions to IOTA since 2008.
Walt Morgan presented an update on the IOTA-VTI and introduced the IOTA-VTI version 3. The VTI was out of production for a few months due a parts shortage and its design was changed. An optional external GPS antenna is available and be attached to each unit. A lithium battery provides a backup power source for the GPS unit.
The key features of the IOTA VTI version 3 are:
Powered by 8 to 28v DC (centre positive)
CCIR (PAL) or EIA (NTSC) compatible
Will work without a camera connected
LED to confirm that a camera is connected.
Internal sensitive GPS is standard
External GPS antenna available
Characters have a drop-shadow – viewable against say, the lunar bright limb
Comprehensive Data Quality Assurance system
Lithium battery give the unit a non-volatile memory
Licensed to IOTA to prevent untimely withdrawal
Price US$249 + shipping
Can be purchased now at http://www.videotimers.com
The units were designed by Dave Gault and Tony Barry of Australia. IOTA has exclusive rights to the units. Currently Walt is the manufacturer. Each quarter, Walt send royalties from the sales to Chad Ellington, IOTA's treasurer.
In March 2014 Globsat, the manufacturer of the 406A Walt was buying, discontinued selling it. They claimed that their new model 506 GPS would directly replace their model 406A, but that was found not to apply to the IOTA-VTI. The more modern PA6H GPS from GlobTop was selected and that has resulted in improved performance. A new circuit board was designed (Version 3) and production was restarted after about a 5 month delay. The new board required a rewrite of the software, which Tony Barry was able to do. To emphasize that there were significant differences, a bone colored case was chosen for Version 3, replacing the black case of Versions 1 and 2.
Since 2011 when the unit was introduced over 400 units have been sold. Most all of the units have been bought by IOTA and "occultationists", including Marc Buie's RECON team. A federal agency in Brazil has bought some units, and even a Norwegian Ski association bought 2 units. It was asked whether IOTA should notify owners of older versions to upgrade to the newer Version 3 unit and offer these people a discount. Walt said this offer should be made perhaps every 6 months through the list server.
For attendees at this IOTA meeting, Walt offered a discount price of $200 USD for the unit. The IOTA-VTI is available for purchase at http://www.videotimers.com.
Treasurer Chad Ellington (presentation made by Roger Venable due to technical problems with Chad's microphone) presented IOTA’s membership status. Currently there are 29 USA print subscribers plus 3 outside USA, 62 online subscribers, total subscribers is 94 with a net decrease of 1 member since last year. The trend of paid IOTA members (print plus online) has steadily decreased in the past few years. Membership totals: 2011:142 members, 2012: 132 members, 2013: 101 members, 2014: 95 members, 2015: 95 members. It was mentioned that the IOTA list sever has over 700 members.
This trend could be explained by the fact that IOTA predictions, methods/techniques and results are all online free. IOTA's Journal of Occultation Astronomy (JOA) is only available to paid members.
Expense report: A summary of the year’s bank balances are:
Starting Balance: $7,544.48 2014, July 2
Ending Balance: $9,608.45 2015, Oct 14 (Includes funds donated for a special
asteroid satellite award)
Net Increase in Balance: $2,063.97 (but $2K is from the donations for asteroid satellite award)
The breakdown of this past year’s budget is:
Membership Income: $600
IOTA-VTI Royalties: $688 up $160 since last year
PayPal Balance: $1417.55....but Chad lets it accumulate to avoid transferring it
back and forth to the bank account and to IOTA-ES
-JOA: consistent from last year
-Web Service: Still Donated
-Awards: $ Not paid for yet
The (JOA) it is getting further behind on schedule. More articles are needed. The new password access for downloading it is working, however many folks have trouble remembering passwords.
This year’s presentation of the annual Homer F. DaBoll award and David E. Laird award was made by the Award Committee Chair Ted Blank. The Homer F. 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. The David E. Laird award is given to people who have made significant contributions to occultation science prior to 15 years ago. Laird (1931-1968) was an organizer of grazing occultations in the early 1960’s. Laird also confirmed the existence of a giant impact on the Lunar far side, The Laird award was conceived to help “catch up” on awards to some older IOTA members.
Previous Homer F. Daboll awardees: 2007: Dave Herald (Australia), 2008: Edwin Goffin (Europe), 2009: Steve Preston (USA), 2010: Hristo Pavlov (Australia), 2011: Scotty Degenhardt (USA), 2012: Kazuhisa Miyashita (Japan), 2013: Graham L. Blow (New Zealand). 2014: Brian Loader (New Zealand)
Previous David E. Laird awardees: 2013: Hal Povenmire (Florida), 2014: Gordon Taylor (England).
This year’s Award Committee consisted of all past recipients (above), Ted Blank (Chairman-Massachusetts) Dr. Terry Redding (Florida) and Richard Nugent (Texas). This year 18 nominations were received – 8 for the Daboll award and 3 for the Laird award, (2 nominations were ineligible). The Committee’s main objective in selecting an award recipient was to reach a consensus and not choosing someone by a majority vote. Eligibility for the award is for anyone who has made significant contribution to occultation science or for the work of IOTA and its goals. Persons not eligible are current IOTA Officers & the award committee. Candidates nominated are not required to have IOTA membership.
The 2015 Homer F. DaBoll award recipient was Austrian astronomer Gerhard Dangl. Gerhard has made numerous contributions to the occultation community with his numerous video camera studies and analysis of rates, frames, internal timing, etc. and his numerous astrometric measurements. Gerhard is also honored by having asteroid 47494 Gerhardangl officially named after him on April 9, 2009.
Gerhard was notified of the award a few days before the meeting and sent a response for the Daboll award to Ted Blank. Ted read it at the meeting.
The 2015 David E. Laird went to Robert "Bob" Sandy of Blue Springs, Missouri for his 55+ years of dedicated occultation activities. Since 1960 Bob has timed 1,189 Zodiacal Catalog stars and over 2,000 non-Z.C. stars, led over 150 grazing occultations expeditions (all with his own drawn pictorial reductions). Bob was one of the first people to notice 0.2 deg discrepancy in the Watts lunar limb charts. In addition Bob has discovered and observed new double stars from grazes. He observed partial planetary occultations of Uranus (2/10/77) and Saturn (11/13/67).
Bob shared some of his memorable observations over his 55+ year occultation career and showed some slides of observers from the 1960's. Bob showed a slide of the "timing cables" used for multiple graze observers. The cable could be laid out for about 1 mile. Each graze observer would have a timing button they would press when they saw an event and it would be recorded by a recording unit at the end of the cable.
This year a Special Achievement Award was given to Rob Lambert of the Las Vegas Astronomical Society. Rob has led numerous expeditions and conducted site surveys for asteroid occultations including the highly successful Sophrosyne event (Nov 26, 2013), Marion event Mar 7, 2015) and several others. Rob arranging the IOTA Las Vegas meeting in 2012 and this year 2015.
The IOTA Lifetime Achievement Award is conferred by the IOTA board of Directors. It’s not an annual award, but done at the discretion of the Board. This time the award is given to Hans-Joachim Bode for establishing both the European Symposium on Occultation Projects (ESOP) and the IOTA/ES Organization, and for his many years of nurturing and growing these institutions to encourage members in many countries to observe occultations and eclipses.
Paul Maley presented his results of the 2015 May 24 occultation of Regulus by Dagmar in Saudi Arabia. The entire path was in daylight except for Saudi Arabia and the Indian Ocean. The logistics from Paul's contacts (hotel, transportation, how many observers, visas, etc.) was sketchy until less than 2 weeks before the event. Due to the unclear plan Richard Nugent and Chuck Herold canceled out of the trip at the last minute. David and Joan Dunham also canceled out to Saudi Arabia but went to Indonesia instead. Paul brought the equipment and showed how the Saudi observers were introduced to the Mighty Minis and how to start the recorders. With 6 sites laid out, only Paul was able to get the event. Other sites had problems run by the students, including pointing to the wrong star and not able to get the Canon recorders started. Two miss observations were also recorded. The student with Paul used his 35mm DSLR camera and actually got the event as shown in a light curve analysis.
Paul showed the occultation of m = +8.4 mag HIP 12740 by 106 Dione as he observed from India in September 2015. This event Paul arranged as part of a tour in which 8 persons went, with the occultation being just side event on the tour. It turned out the actual site Paul used near a lake had cars running their headlights, people all over and even pigs walking around ! To add to this mess 2 minutes before the event people had started fires at the edge of the lake in the direction of the target star. The observational results were 2 positives and even a miss observation from someone in China who happened to be just outside the predicted path edge.
Paul showed the Southwest Research Institute (SWRI) target events for 2016. Currently there are no funding for these events but this could change. Paul showed their #1 priority event 283 Emma for April 16, 2016 with an m = +8.9 mag star. Nine other events were shown. Many of SWRI events have moons with poorly known orbits, hence the need to observe them.
Steve Conard presented results of the spectra of an occultation from Jupiter's moon Europa occulting Io from May 11, 2015. Steve used a Celestron 14-inch telescope with a Shelyak Alpy Spectrometer. Alignment of the moons from the 3 arc-second wide slit was good and he recorded at 5-second integrations. He collected data for 30 minutes before and after the event. The observations showed that there was much noise associated with the spectral curves before during and after the occultation. In addition some clouds impacted the signal level at event time. Jupiter also contributed stray light. Steve postulated next time he tries this type of event there are some ways to minimize this in the data analysis.
Drs. David and Joan Dunham next presented a summary of their trip “down under” in Australia. The Dunhams have been to Australia several times since 1980 and he first met Dave Herald in 1986 while attempting to observe the occultation of a m = +6.8 star by Halley's Comet during a total lunar eclipse.
David had designed some of the software of the MESSENGER spacecraft mission. When it crashed on Mercury on April 30, 2015 his duties were over and the very next day he left for Australia. Some of his goals while there in addition to sightseeing was to promote occultation science, observe some special occultation events and develop improved observing and equipment techniques. He also attended the 9th Trans-Tasman Symposium on occultations in New Zealand during this trip.
On May 21-28, 2015 he went to Sumatra/Indonesia to attempt the Regulus occultation by 1669 Dagmar. At Paul Maley's Saudi site, the University could only support 6 stations, leaving Dunham to attempt it from Sumatra. With only a 5 degree altitude of Regulus, only 1 of 4 stations the Dunhams setup was able to record the event. The event was barely detectable due the atmospheric conditions and low altitude. Tony George and Brad Timerson were able to extract an occultation from the data.
The next day they flew to Yogyakarta to observe the Delta Sagittarii occultation by Jupiter. Five of six planned sites were manned but cloudy conditions prevented the observation to all but 2 westernmost stations.
May 29 - he attempted a Venus Occultation from Brisbane of m = +6.2 HIP 79580. The glare from Venus foiled the visibility of the event.
June 18 - occultation of a m = +12.3 star by 145 Adeona. The Dunhams ran 2 stations and Richard Williamson observed from his observatory. No stations had an occultation.
Other events he attempted: June 29 an occultation of an m = +12.3 mag star by Pluto. Clouds forced him to move and he reached clear sky 20 minutes before the event but hadn't the time to lock on the target. The occultation was observed by the SOFIA satellite from the predicted central line s.e. of NZ with a good recording of the central flash. Although some stations were clouded out, several recorded the event from New Zealand & one from Tasmania. D. Herald at Murrumbateman, NSW had the closest miss observation.
July 17 occultation of m = +11.9 mag star by 266 Aline. Two out of six stations got positives on this event, batteries failed with the other 4 stations.
August 2-14, he attended the IAU convention in Honolulu. See more about the conference below in the Sunday talks.
Aug 22, 100 Hekate with m = +10 star. Dunhams ran 8 stations. 5 stations had positives, 3 stations were misses. This resulted in a good profile.
Sep 5, occultation of m = +12.4 mag star by Artemus. He had 2 successful occultations. An integrating camera had to be used to bring out the faint star.
Sep 11, occultation of 9.2 mag star by 233 Asterope. They ran 11 stations, 7 stations were positive, 3 stations had a miss and 1 station's battery was too low at event time. This was Dunham's most successful multi-station event.
Oct 8, an occultation of Venus by the 15% Moon with an attempt to record the Ashen light. His recordings showed no indication of the Ashen light.
Dunham next discussed his previous-night pre-pointing with paver mounts. John Broughton designed a "paver mount" which utilizes a typical backyard paver patio stone. An altitude-adjustable cradle is attached to the 12" wide paver stone. The heavy 20+ pound (10 kg) weight of the paver stones make for a sturdy mount sitting low to the ground with hardly any visibility from the road.
His first attempt with these mounts was the June 22, 2015 m = +5.1 48 Leonis graze with 6 stations. Two stations were successful.
Next attempt with the paver mounts was the July 31 event with 420 Bertholda occulting a m = +10.3 star. Four paver mounts were set up and with 2 attended stations, 1 paver station had a positive. One of the stations (Station 4) was apparently attacked by an animal and hence got no event !
Sep 30, 697 Galilea occultation of an m = +6.3 star. Paver stones weren't available, so they used corkboard. The corkboard was nailed to the ground with nails. Unfortunately no stations had a positive which included several in New Zealand. The stations had the usual problems - clouds, battery failure, scope mount kicked by mistake and recorder didn't work.
Steve Preston spoke about this evening plans for the stations for tonight's occultation by (215) Oenone. At meeting time, the weather indicated clouds and thunderstorms with only a slight chance of a hole in the clouds. (The event was clouded out in the Las Vegas area. Only 1 chord was obtained by Dr. Richard Nolthenius in California)
9:00 AM Saturday, Technical Sessions continue
Bob Sandy passed around an eyepiece he made with a protractor grid allowing the observer to know in advance the cusp angle of a reappearance event.
While internet technical problems were being fixed, the onsite attendees then introduced themselves.
Dr. Roger Venable presented a perspective of the 2002 solar eclipse observation of Baily's Beads. Roger observed Baily's beads in Dec 4 2002 in the outback of Australia with 4 telescopes with different narrow band filters using a quad recorder. Roger could view in real time each video simultaneously on his monitor. There is an issue in seeing the actual eclipse real time on the monitor with the different filters vs. later on from the video recording. For example an image on one monitor was bright so he turned down the gain for that camera. However upon examining the video after the eclipse, turning down the brightness on the bright image gave a black background on another recorder using a different filter. Hence some data was lost. His observation of this eclipse was used by David Dunham in his solar radius calculations.
Roger showed a graph from a 2012 paper (Raponi, Sigismondi, et. al) from the Jan 2010 eclipse. The disappearance and reappearance of a particular bead from observations by Richard Nugent (Uganda) and Andreas Tegtmeier (India) was analyzed. The paper suggested that inflection points on the graph indicates where the solar limb was. However this limb was may not be the actual solar edge as different wavelengths transmit different solar radii. Roger offered several reasons why bead observations have problems in determining the solar radius, namely color differences at the limb, diffraction, Mei scattering by electrostatically elevated dust at the limb and issues with the bright inner part of the chromosphere.
Roger's analysis of the color differences at the solar limb suggests that a different measuring approach be taken at future eclipses. He proposed obtaining photometry of the Beads in both the red and blue wavelengths, using a large aperture telescope to minimize scintillation during photometry and obtain low resolution spectra of Beads while simultaneously acquiring photometry. Later in the day David Dunham proposed that IOTA begin its preparations and techniques to prepare for the Aug 2017 total eclipse over the USA.
Steve Conard (with Bruce and Dylan Holenstein) talked about progress and testing on emCCD (electron multiplying CCD) camera testing. In 2015 Conard and Bruce Holenstien observed some lunar occultations. Their limited time available made them unable to attempt any asteroid events. On Feb 28, 2015 they observed the Lamda Gemini occultation by the Moon. The Tangra graph showed 13 transitions in brightness in the 0.3-sec before disappearance. The sampling rate was 200 Hz. Steve pointed out that it is exceedingly unlikely that the occultation geometry could support such transitional events, and the 200 Hz sampling would have to produce many more partial levels than we are seeing. The observed transitions he concluded was an instrumental effect and not a real effect. With new equipment Steve will investigate dependence of wavelength on the high speed data.
Steve is observatory director for the new Roelke Observatory near Westminster, MD. This has a 14″ SCT on a heavier mount than Conard’s own Willow Oak Observatory, and should allow for heavier payloads. Steve likely will soon have access to a 0.6m R-C telescope at his place of employment. They are trying to obtain access to a 0.8 m R-C at a Baltimore area university as well. All these potential telescopes should allow us to test these heavy cameras on relatively larger apertures. The team will continue to look to try faint TNO events.
- - break - -
Elizabeth Warner presented an update on the Astronomical Digital Video System (ADVS) at the University of Maryland. Ms. Warner is the Director of the University of Maryland Observatory operated by the Astronomy department. She got the video system running and made their 1st observation of 2015 on Jan 10 with the asteroid occultation of 489 Comacina.
Several problems arose - one cable broke due to the cold weather, and they couldn't change the frame rate. Michael Barry and Dave Gault helped work on this issue. Several more asteroid occultation events were attempted in 2015 including the 46441 Mikepenston event on Sep 8. Elizabeth was on vacation during this event but she had trained 2 students to work the equipment who were successful and got a 1/2 sec occultation. A 3.75 frames/sec rate was used for this recording.
Steve Preston presented an analog video capture with PC’s. It works with Windows 7/8/10, and Virtual Dub and uses the StarTech driver. Total hardware and software cost is around $200. The system records to an AVI file. The system has Manual mode with a stop/start option and a timer mode with a start stop via the timer. Recording time is 30 minutes without an SD card. Steve showed some tips on how to run the system and viewing and analyzing the AVI files.
Bob Sandy asked how one would determine if frames are dropped. Tony George mentioned that one could use the R-OTE, OCCULAR and AOTA programs to examine the VTI output to compare corresponding frames.
-- lunch break --
Ted Blank presented how he generates pre-point charts with Guide, and experiences in using them. Pre-pointing is the way to have your telescope pointed on the target star at the time of the occultation without any motor drive, polar alignment, etc. The technique involves pointing at a field long before the event. The telescope will remain fixed in place. As the Earth rotates, the target star will drift into the FOV at the time of the event. As an example if you're setting up a telescope 1 hour before the event, you would point your telescope at a field 1 hour in RA less than the target star RA.
Pre-pointing is superior to a motor driven telescope as no polar alignment is needed, no motor drive is needed and visibility of the target star is not necessary. Pre-pointing allows you to pre-point to a much brighter star at the same/similar declination with a lower right ascension .
Guide is the recommended software to make pre-point charts. Version 9 of Guide is now freeware and Ted brought a few copies on DVDs to pass out to the on-site attendees. Ted showed how to use Guide and its options to set up the pre-point charts. A typical Guide chart will have a line with time tic marks. The tic marks will have times marked (a time line) for a particular event. If your telescope is pointed at a FOV at the time marked by the time on the tic mark, then it will be pointing at the target star at the moment of the occultation.
Ted then continued with how to make pre-point charts and using them in the field. Some common sense pointers: don’t print charts with times prior to sunset, use equatorial charts if your telescope is equatorially mounted, use alt/az charts if your telescope is on a tripod. Don't use a laptop as a chart - the screen will be too bright ruining your night vision and it’s helpful to have some overlap with adjacent charts. Printing charts several days before the event allows you to practice and identify easy stars that you find in the process. A wristwatch that you use should have accurate time and be backlit to be able to see the time at night.
Ernie Iverson spoke about Avisynth scripts useful in occultation work. Avisynth is a macro that opens/post processes recorded videos with a variety of options. Ernie showed an occultation example of 96 Aegle from 2010 in which he originally reported a miss. Later on he found out he had an occultation by viewing it on a larger screen. The functions discussed enable the observer to better see various parameters associated with their video recording.
Some options Avisynth offers are brightness and contrast controls, scale factor changes, noise reduction, etc. Avisynth opens videos without creating extra files.
Avisynth can be created as a text file and saved as an avs file. In Limovie under the button "OPEN AVI FILE", the user would click on the avs file (located in the same directory as the video) and Limovie will open the video. Ernie explained the particulars of what functions/plug-ins need to be entered into the avs file, such as the file name, its path. The function DVInfo is used to display the Canon ZR camcorder time stamp to resolve issues with inserted time code. The function LanczosResize changes the aspect ratio of the video to match the sky since many DVR's change the sky’s aspect ratio when recording usually by some compression scheme which isn’t uniform in both vertical and horizontal directions of the video. Another function Ernie mentioned was very useful is the Level filter. This one adjusts the brightness/gamma of the video. He suggested setting the gamma to 1.0 and leaving it alone. The Coring function relates to the range of input pixel values, he suggested setting Coring to "False" and then leave it alone. By changing the range of pixels set to pure black and pure white the Level filter will increase the brightness of the pixels and reduce the noise making fainter stars visible.
When Ernie applied the various enhancements to his 96 Aegle occultation video, the occultation came out. Ernie also mentioned the "AddThree" function written by Steve Preston. It integrates either 3, 5 or any odd number of frames you want. This function integrates the video by adding adjacent frames. Since multiple frames are combined there is a time synchronization issue.
The Magnify function enlarges a user defines portion of the video. In particular for double stars, if the stars merge, the magnify function can help separate the stars for positional measurement.
Executive Secretary Richard Nugent presented a video drift method to measure double stars that he and colleague Ernie Iverson have used for the past 5 years. The method uses the same equipment and software as for an occultation observation – telescope, video camera, VTI, digital video recorder and Limovie software for reducing videos.
In 2010, Richard noticed that Limovie’s output CSV file (in additional to listing brightness data) also lists the (x,y) coordinates of up to 3 target stars for each video frame. This was all he needed to know to determine that he was going to start measuring double stars for position angle and separation. A major advantage of the technique over any other method is the large no. of data points generated by short 25-30 sec videos. At 30 frames/sec a 30-sec video produces 900 (x,y) pairs for analysis with each frame generating a position angle and separation which are averaged.
Thus far Nugent and Iverson have published over 1,100 double star measurements in the Journal of Double Star Observations (JDSO). With their respective 14″ SCT telescope equipment, they have a scale factor of 0.6″/pixel and have measured doubles down to 3.5″-5″ separation, typically with separation standard deviations averaging 0.37″. In 2014, Iverson devised a modified drift method that now allows the measurement of doubles down to m = +17 and fainter, thus tripling the number of doubles within reach of the telescopes.
Nugent showed videos of how the modified drift method works using an integrating camera to reach faint doubles. First the integration is set to reach the faint doubles with the telescope's motor drive on (16 frames combined for example). With the video still running the integration level is brought down to 30 frames/sec and a brighter nearby star at the same or nearly the same declination is brought into the field and allowed to drift several times across the FOV. All along the video continues to record. The motor driven integrated portion of the video allows measurement of the PA and separation of the double star in arbitrary units while the drift portion allows the computation of scale factor and drift angle.
To get the PA and Sep of the double star, the user will manually enter the drift angle and scale factor from the drift phase into the reduction program Vidpro (VIdeo Drift Program ReductiOn). The modified drift method was presented at the SAS conference at Ontario CA in June by Ernie Iverson.
Dave Herald next talked about archiving occultation light curves in Occult -- a software update. Dave started out by describing how historical lunar occultations were archived. In the latter half of the 1900's considerable interest developed in discovering double stars from lunar occultations. Many (70%) of these suspected doubles from occultations were caused by diffraction effects and the large stellar diameters. Many suspect doubles were verified by modern video camera recordings at frame resolutions that far exceed those of the visual observers.
Around the year 2000 video recordings became common and are the standard today. Limovie was released in June 2005 and revolutionized occultation data reduction. Tangra, another occultation video reduction program was released in 2009 by Hristo Pavlov. The use of these programs has helped identify, verify and discover double stars. In addition the programs could analyze gradual light curves and distinguish between stellar diameter and Fresnel diffraction.
In seeking a method to archive IOTA's light curves, Dave has been in contact with the folks who run the VisieR astronomical data base. They have been very supportive to us in archiving our light curves. So the challenge is what data needs to be collected with a light curve. What will be needed for any investigator to examine the light curve/data is (at the very minimum) the date, light curve duration, star ID, lunar libration/limb slope, observing location and observer name.
Currently Limovie can save a light curve into the clipboard. Whatever method used to archive light curves/reports, it must be easy to use. The method and data format must be able to consolidate reports, be user friendly and deal with spam issues and be able to meet VisieR requirements.
Dave next talked about the discovery of the radio source 3C273 and the first extragalactic jet. 3C273 is known as the 1st quasar, 1st radio jet, 1st inverted spectral radio source, 1st radio and variable spectral source, and the 1st black hole. A Hubble image clearly shows to the lower right of the star-like object an optical jet.
People involved in the discovery were Cyril Hazard, Maartin Schmidt, John Bolton, W. Nicholson and Tom Matthews. Telescopes involved were the 200-inch at Palomar, Parkes and OVRO radio telescopes.
3C 273 was a radio source whose position was not known accurately. An occultation occurred on August 5, 1962 in which an emersion and immersion occurred of the radio source. John Bolton communicated a position to Maartin Schmidt supposedly with a precision of 0.2″ in DEC and 0.1s in RA of the “B” component but this position had problems and could have been 10″ off. Another occultation occurred on October 26, 1962 with the Parkes radio telescope and in early 1963 Hazard wrote to Schmidt with the correct occultation positions for A and B components and suggested a joint publication. This core-jet radio structure now coincided very closely with the optical image. Component B was now clearly identified as the bright STAR counterpart in the optical image.
In February 1963 Maartin Schmidt examined the spectra of the optical counterpart of the radio source and was puzzled that none of the absorption lines matched the laboratory comparison spectrum. He finally realized the Hβ, Hγ and Hδ lines of 3C 273 were red-shifted approximately 16%. This indicated a redshift of z = 0.16. The result was published in a letter to Nature for March 1963 and this discovery has forever changed astronomy.
Herald next presented asteroidal occultation results since the last meeting. About 200 asteroid events are being observed each year. A slight decline from 2010 occurred but 2014 was a record year. He presented statistics for the 2014 successful asteroidal occultations by region - Japan, Australasia, Europe and North America.
He mentioned the discoveries from asteroid occultations: asteroidal satellites, double stars and rings around 10199 Chariklo. A satellite discovery (unconfirmed) on Jan 19, 2012 of 911 Agamemnon occurred in the USA. Although this discovery is unconfirmed, the evidence indicated a real satellite and a paper was published in Planetary and Space Science for March 2013 entitled "Occultation Evidence for a Satellite of the Trojan Asteroid 911 Agamemnon". A second discovery (also unconfirmed) was on Aug 3, 2013 of 2258 Viipuri. Dave next showed a profile of rings discovered around the asteroid 10199 Chariklo.
Dave showed plots of several inversion (light curve) models of several asteroids including 25 Phocaea, Pallas, Geographos, 9 Metis (2 models) and 135 Hertha from Dec. 2008. Currently over 2,700 asteroid occultations observations have been observed and archived. This includes 12,600 observations (many are misses). This comes to an average of 5 observations per event.
The regional coordinator collects occultation events and analyzes them for completeness and forwards this info to the global coordinator who is currently Dave Herald. He periodically sends a report of astrometry derived from occultations to the Minor Planet Centre – with all associated observers being named, and this information is included in the SAO/NASA ADS (Astronomical Data System). All asteroid reports appear (after a comprehensive review process) to NASA's online Planetary Data System. This data set is submitted to NASA by David Dunham and Dave Herald.
Dr. David Dunham presented a Report on 29th general assembly of IAU in Honolulu from August. The IAU meets every 3 years and is the premier organization of professional astronomers. Several symposia were presented including one on “Asteroids, New Observations and New Models.” Also a presentation was given on the Gaia mission results.
David gave 4 poster presentations, Sizes, Shapes and Satellites from Asteroid Occultations, Double stars from asteroid occultations, Solar diameter results from total and annular solar eclipses and Plans for the 2017 August 21st total solar eclipse. David mentioned Scotty Deganhardt in the asteroid occultation paper whose modified multi-station deployments has revolutionized asteroid occultation events. The posters also showed the 90 Antiope binary asteroid profile, and the 3D inversion shape models compared to occultation profiles.
One poster presentation was close double stars discovered from occultation recordings for Commission 26 on Double Stars. It included a paper in JDSO Double Stars discovered from Lunar Occultations and double stars discovered from asteroid occultations.
He also presented Solar Diameter Measurements from Eclipses since 1970 at the path edges. The talk included solar diameter determinations from eclipses up until the Aug 2008 eclipse. His final poster presentation was Plans to Observe the 2017 Total Solar eclipse. He showed Ted Swift's May 2012 Baily's Beads video frames.
Two occultations occurred during the General Assembly. A grazing occultation event Aug 5 by the m = +6.5 star 96 Piscium across southern Honolulu. For Aug 13 a possible asteroid event with a +9.6 star by 1197 Rhodesia would occur. Ernie Iverson prepared the pre-point charts for this event. David got a miss from his location and the single successful event was made by Bart Billard in Fredrickburg, VA using the CCD drift scan.
Meeting ended 6:30 PM. Attendees continued discussions at a local restaurant.
9:00 AM Sunday – Technical sessions continue
Karsten Schindler presented Occultation work with SOFIA and the University of Stuttgart's 60 cm (24-inch) telescope. He showed a slide of SOFIA in flight - it has a 2.4 meter telescope that can be used with the door of the plane open. SOFIA is a modified Boeing 747 that flies at 850 km/hr. At this speed, the telescope has to be de-coupled from the plane's vibrations. This is done with special springs keeping the telescope suspended. Observations are typically done from 39,000-44,000 ft. Flight plans for each flight have to be approved by the FAA and flights can typically last for 8-10 hours. Currently about 2-3 flights are made each week with an annual cost of about 74 million dollars.
SOFIA has the several instruments -
HIPO - High Speed Imaging Photometer for Occultations,
FPI+ - Upgraded Focal Plane Imager, can image to 400 frames/sec down to m = +16 making it a very fast photometer. FPI+ works so flawlessly it is now a permanent SOFIA instrument.
SOFIA observed the Pluto occultation June 23, 2011. The flight path took it over the mid-Pacific ocean where it observed the occultation. The timing was critical to observe the central flash - the plane must be within a 100km zone at the center of the path and within 1-minute of the mid-event. All this while traveling at 850 km/hr ! The star being occulted was m = +14.6. Karsten showed a video of this event. The resultant occultation light curve profile was published in the Astronomical Journal (AJ) in 2014. The central flash was only barely visible on the light curve as a gentle rise in the light curve at mid-event. This indicated a level of haze in Pluto's atmosphere.
Another Pluto occultation occurred June 29, 2015 just 2 weeks before the New Horizons mission flyby. This star was m = +12.1 and the occultation path was south of Australia. He showed a video of this event which clearly showed the central flash. The light curve also had a spike at mid-eclipse showing the central flash.
Karsten next showed the Sierra remote observatory located 50 miles South of Yosemite National Park and about 50 miles North of Kings Canyon National Park in the Sierra Nevada Mountains of California. It includes some 10 roll off roof observatories. The 60cm (24-inch) telescope he uses there is controlled remotely. The telescope is used for photometry, astrometry and is a hardware/software test platform for SOFIA. Since Sept 2014 they have observed 16 occultation events. The camera system used can time stamp each CCD image frame (up to 202 fps 32x32) and down to 9 fps at full frame resolution at 0.56"/pixel. The first positive occultation was 34 Circe on Oct 7 2014. His chord was one of 2 positives for this event.
Karsten mentioned some future plans he has in mind - including determining the sizes of some of Jupiter’s 50+ moons using the occultation technique.
Brad Timerson presented the best observed North American Asteroidal events of the last year through July 2014 thru September 2015.
24 August 2014 393 Lampetia – 5 chords
6 September 2014 93 Minerva – 9 chords, has known satellite
18 September 2014 82 Alkmene – 4 chords
20 November 2014 3 Juno – 2 chords
10 December 2014 127 Johanna – 2 chords
10 January 2015 489 Comacina – 5 chords
10 January 2015 786 Bredichina – 4 chords
20 January 2015 702 Alauda – 4 chords
30 January 2015 166 Rhodope – 5 chords
18 February 2015 71 Niobe – 5 chords
7 March 2015 506 Marion – 10 chords!
2 April 2015 90 Antiope – 14 chords, double star
15 April 2015 595 Polyxena – 5 chords
6 May 2015 107 Camilla – 3 chords
20 June 2015 426 Hippo – 4 chords
17 July 2015 679 Pax – 3 chords, 2-model fit
23 August 2015 107 Camilla – 6 chords
4 September 2015 409 Aspasia – 5 chords
For these events Brad showed the shape profiles and inversion model comparisons when available. The 90 Antiope event of April 15, 2015 had 23 positive chords once again showing both binary components.
Brad next presented “How well do inversion models fit historical asteroidal occultations?” Some issues he examined are: do present modeling techniques fit old events?, does one model fit better than another? Regarding multi-Year Model Fits, How do models fit the same asteroid over time?
Inversion models have only been around for 6 or 7 years. IOTA has asteroid profiles gong back 40+ years. Brad pulled some older asteroid profiles including Juno (Dec 3 1979), Pallas (May 29, 1983, 235 chords) and overlaid them on modern day inversion models and the fits were excellent. This considering that many earlier occultations were visual ! He then showed model fits for asteroids with multi-year model fits. The fits were good, remembering that the asteroids have rotated and changed their orientations. Some model fits spanned 7 years, and 93 Minerva's models spanned 32 years with excellent fits from 1982, 2010 and 2014 !
- - break - -
Steve Preston next presented the best asteroidal occultations upcoming in late in 2015 and in 2016 over North America. They are:
October 30, 2015 415 Palatia
November 7, 2015 778) Theobalda
November 11, 2015 29 Amphitrite
January 22, 2016 115 Thyra
January 24, 2016 866 Fatme
Binary April 4, 2016 216 Kleopatra
August 27, 2016 85 Io
September 3, 2016 51 Nemausa
September 8, 2016 224 Oceana
September 14, 2016 372 Palma
September 14, 2016 487 Venetia
October 31, 2016 814 Tauris
Dr. David Dunham next presented Upcoming total and grazing lunar occultations (especially Aldebaran). David first mentioned that Dr. Richard Nolthenius got a positive occultation from Friday nights 215 Oenone event and he may be the only observer that had one since the Las Vegas area was clouded out.
David showed graze maps from the RASC Observer's Handbook. He mentioned just 2 good grazes remain for 2015 over North America:
Aldebaran by the full Moon Nov 25, 2015.
Dec 6 2015, by a m = +4.4 star over southern Arizona, New Mexico and Texas. 2016 grazes include a naked eye graze of Aldebaran July 29, 2016. David suggested we might advertise this event and schedule IOTA's presence there.
Another Aldebaran graze occurs October 19 with an 87% sunlit Moon. The path goes over southern California, Las Vegas and up thru Canada.
The meeting ended at 11:55 AM.
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.