The International Occultation Timing Association's 39th Annual Meeting

July 17 -18, 2021 via Zoom online

by Richard Nugent, Executive Secretary

 

 

The meeting presentations, Zoom link agenda and schedule for this year are located here:

http://occultations.org/community/meetingsconferences/na/2021-iota-annual-meeting/

Ted Blank was in charge of the techncal operation of the Zoom meeting throughout. Thank you Ted !

 

  ..........................................Homer F. Daboll, David E. Laird and Lifetime Achievement Award winners:

                                                              

     Description: C:\Users\Owner\Desktop\myweb\IOTA2021-1.jpg       Description: C:\Users\Owner\Desktop\myweb\IOTA2021-2.jpg     Description: C:\Users\Owner\Desktop\myweb\IOTA2021-3.jpg                                             

Homer F. Daboll Award: Bob Anderson         David E. Laird Award: Richard Wilds           Lifetime Achievement Award: Roger Venable  

 

Attendees: The meeting had a total of some 83 participants and this number fluctuated slightly throughout the sessions.

 

 July 17, 2021 20:00 UT – Meeting start

 

Vice President Dr. Roger Venable  opened and welcomed everyone to the meeting. Ted Blank gave instructions for using Zoom functions for this year’s fully online meeting.

 

Business meeting:

 

Treasurer Dr. Joan Dunham presented IOTA’s financials and membership status. A summary of the year’s income/expense report (July  2020 to July, 17 2021):

 

Income:

  • Membership  …………………...........…$2,738.54
  • Royalties (VTI & RunCam sales)............$7,269.91
  • Donation...................................................$1961.20
  • TOTAL INCOME....................................$11,969.65

Expenses:

  • JOA Production.....................................$1078.17*
  • VTI Production......................................$3510.49
  • Other......................................................$618.07
  • TOTAL EXPENSES..............................$5206.73

NET Income: $6,762.92

 

*Note: IOTA has not yet been billed for production expenses for JOA 2021-3  

 

IOTA Balance Sheet

 

Cash on Hand - Bank and Paypal..........................$17,234.49

 

MADAMO AWARD...............................................$4,000.00 - Funds dedicated for asteroid moon discovery and confirmation

 

Reserve Fund - Web Server.....................................$500.00

Net Worth...............................................................$12,794.39

 

 

IOTA Membership and Subscription:

Membership only -118

Affiliate membership - 5

 

IOTA Affiliate membership: IOTA’s has an affiliate membership which is a non-voting membership for organizations, schools, clubs, businesses but not for individuals. It allows widespread distribution of event information – such as bright stellar occultations by asteroids, bright grazing occultations, etc. This membership will renewed annually and is free of charge but requires a renewal certification that the membership is for a group of at least 2 contacts. Rather than make an Affiliate Membership web page which has the potential for spammers, Joan will rely upon referrals for new affiliate memberships.

 

This past year donations were received by the following:

David Dunham - to complete funding of the MADAMO asteroidal satellite discovery award

Berton Stevens

Joan Dunham

Dwight Smith for the Occultations user Group Administration

Julie Rausch, in honor of Walter Morgan

 

And of course non-cash donations were made by many, spending many hours on observing activities, data analysis, software development and maintenance, IOTA administration, outreach activities, web site maintenance, and more. To everyone who donated to IOTA this past year: THANK YOU! Your support is key to IOTA’s success.

 

 

Executive Secretary Richard Nugent presented IOTA’s Homer F. Daboll, David E. Laird and the Lifetime achievement awards. The Homer F. DaBoll Award is given to recognize significant contributions to the field of occultation science and to the work of IOTA. This year's recipient is Bob Anderson from Oregon. Bob emphasized the statistically rigorous computation of occultation timing parameters. In 2007, at the suggestion of Tony George. Bob developed the program Occular to reduce occultation light curves using the method of least sqaures. Bob then later developed R-OTE to replace Occular. In 2017 Bob introduced PyOTE at the IOTA annual meeting. PYOTE is a multi-platform program to replace Occular and R-OTE. It works with Windows, Mac and Linux. He then introduced PyMovie. Bob also developed the program ArtStar – to test CCD cameras by introducing an artificial star to simulate occultations.

 

Bob sent the following message upon his notification of the award:

 

Thank you for this award. It is an honor to be included in the group of prior recipients of the IOTA Homer Daboll award.

 

I can easily trace my involvement with ‘things IOTA’ to a specific date: on June 7, 2007, I was on a plane headed to Florida to observe a Shuttle launch (STS-117) scheduled for the next day (and it did launch!). I was accompanied on that trip by Tony George. During the flight, he explained the difficulties he was having using Excel to extract D and R times from occultation light curves. It was then that I uttered those fateful words: “Maybe I can use what I know about extracting known-shape signals from noise to help with that”. Tony may have responded with: “Great, when can you have it done?”

 

From that conversation soon flowed Occular, with R-OTE, PyOTE, and PyMovie following at a more sedate pace in the following years. Much of the development of those programs was guided by Tony’s suggestions of ways in which the programs could be made easier to apply to the issues faced by occultation observers.

 

I had thought that, by this time, I would be doing only routine maintenance on PyMovie and PyOTE. But with the work that Dave Herald has done in making the Gaia catalog accessible and Steve Preston’s increasingly precise predictions, I realized that it was likely that there would be more occultations in which diffraction would need to be taken into account, so I undertook a project to add diffraction effects to the model light curve used by PyOTE; this is the subject of a talk that I will give tomorrow.As I prepared the diffraction talk for this meeting, I realized that with the Gaia/prediction advances, a tool that I used in my diffraction studies - calculation of the diffraction pattern of an arbitrary shape object - may be useful in analyzing observations of asteroids with ‘companions’ (which will have interacting diffraction patterns), so I am contemplating a future project to make that tool available as a separate program.

 

Thank you again for this award.

 

 

 

The David E. Laird award is given to recognize those who, more than 15 years ago, made significant contributions to occultation science and to the work of the IOTA. This year’s David E. Laird award recipient is Richard Wilds from New York.

 

Richard was a major graze observer and organizer and did extensive work with grazes and occultations in the 80's and 90's in the Kansas City area. He and Craig and Terry McManus (former IOTA Secretary-Treasurers) were the first IOTA folks to put together an image intensifier in the 90's to reach fainter asteroid events. Richard has also done numerous TV interviews to introduce upcoming occultation events. In 2008 he published a labeled version of  "The Marginal Zone of the Moon" from Chester Watt’s original charts of the lunar topography. He published an extensive article recently on "Lunar Grazing Occultations" in the Encyclopedia of Lunar Science. Richard has published numerous articles in both magazines, astronomy newletters and professional journals. From Sky & Telescope: ”Mapping Asteroid Shapes by Video”, “Observing a Solar Eclipse from the Edge”, (plus numerous other articles on bright and dark nebulae). An Astronomy magazine article from 2018, Richard described the RunCam camera and how to use it for video: “IOTA RunCam Night Eagle Astro Edition”. In 2017, Richard received the pretigious Donald E. Osterbrock Book Prize, for the Biographical Encyclopedia of Astronomers by the American Astronomical Society, Historical Astronomy Richard also published the book: Bright and Dark Nebulae: A Guide to Understanding the Clouds of the Milky Way”, CreateSpace, 2017

 

Richard sent the following message upon his notification of the award:

 

I want to thank everyone for the honor of being selected for the IOTA David E. Laird Award. In Dr. David Dunham’s educational travels through universities such as Yale and Texas, he would spend part of his time in the 1960s at the United States Naval Observatory (USNO), and it was at the USNO that he produced the first effort at a Manual for Grazing Occultations. It is interesting that this first Manual included something similar to the 1960s Mission Impossible quote –“Should you or any member of your team have difficulty with any law enforcement agency, then the USNO and the U.S. Government will disavow any knowledge or association with your efforts.” How could any person looking for adventure in science ignore such an offer!

 

I did not have a Driver’s License, so I volunteered to draw the early Lunar Grazing Occultation Profiles to help Graze Leaders and joined Lunar Grazing Occultation Expeditions as an observer. Once I obtained my Driver’s License, then I began my Graze Leader efforts of several hundred Lunar Grazing Occultations. I spent a number of years in the 1990s as IOTAs Grazing Occultation Coordinator. There were also Solar Eclipses from the Edge, Asteroid Occultations of Main Belt and Jovian Trojans along with Jupiter and Saturn Mutual Events among their moons. Perhaps one of the more interesting moments came with a phone call from NASA at 1AM one morning demanding assistance with the Lunar Reconnaissance Orbiter mission. They were trying to coordinate ground based images with the LRO imaging from Lunar orbit and needed help in identifying what they were imaging. They had heard that I was a Lunar Limb specialist and asked me to identify the objects in their images. By 1:30AM I had been able to identified multiple craters that had appeared in their view.
The main point of it all is that IOTA has provided me with the framework for service in the pursuit of knowledge in science. We all have an opportunity to accept the mission! Remember, should you or any member of your team…

 

The IOTA Lifetime Achievement Award is given, as needed, to recognize outstanding contributions to the science of occultations and to the work of the International Occultation and Timing Association over an extended period of the recipient's lifetime and is conferred by the IOTA Board as needed. This year's Lifetime Achievement Award 's recipient is Roger Venable from Georgia. Roger has observed asteroidal occultations for 33 years, including 100's of multi-station deployments. This includes over 770 stations set up (at the time of this writing), many of which were unattended video stations. With 306 occultation events observed, he obtained good data on 572 stations and 199 stations that didn't get good data. Roger authored Chapter 10 of the IOTA manual, “Unattended Video Stations”, refining the drift thru technique.

Roger has made especially long trips for near-Earth asteroid events during the last two years, helping nail down first the orbit of Phaethon. He did the same for the smaller and more threatening Apophis, verifying its orbit by recording occultations on March 22 and April 4th from multiple stations – adding orbital precision that shows that Apophis will miss the Earth during its several close approaches for at least the next 100 years. He also drove 2,647 miles (4,240 km) for the May 2012 annular eclipse in California (Georgia to California). Roger is also very active in ALPO and is the Mars section coordinator. Roger is a retired physician, having practiced family medicine and emergency medicine for 43 years.

 

For information on IOTA's awards, including previous awardees, see the award webpage:

http://www.asteroidoccultations.com/observations/Awards/IOTAAwards.htm

 

Technical sessions:

 

 

President Steve Preston presented a list of the best asteroid occultations of the coming year. He picked events (not necessarily because a bright star was occulted) based on larger asteroid sizes and favorable ground coverage. One of the anticipated events is by 6 Hebe across the USA later this month on July 26, 2021. Paul Maley observed the occultation by Hebe in March 1977 and he reported a short blink from north of the actual path, indicating a possible satellite of Hebe, hence the need for additional occultation observations to possibly see if such a satellite exists. Several events by Hebe will occur of the next few months and observers are encouraged to make the effort to observe them.



Bill Hanna next spoke about a remote permanent observatory. Bill made his first occultation observation some 10 years ago. He lived in Australia for many years (now he lives in Montana) and chose a site in Australia for his remote observatory. The observatory houses 7 telescopes. He equipment consists of a 20-inch Planewave f/6.8 telescope, with Paramount ME II absolute on-axis encoders, QHY174m camera, and Compulab IPC2 i7 computer. All the equipment was cheaper to buy in the US, but with all the hassles of mailing, customs, etc. he decided to buy the equipment in Australia. Most of the equipment is mounted on the telescope. Bill showed several photos of his setup.

Bill runs the whole system off his Asus gaming laptop (because of its computing power) and typically can have the whole system turned on and running for data collection in 15 minutes. The MPA Home Page Bill uses to monitor the operation has an all-sky camera, observatory webcam, weather status and an observatory roll-off open/closed status.

In the past 3 years, Bill has scheduled
1278 occultation events
He sent in 532 reports
410 - misses
122 - positives

Going forward, Bill plans to be doing astrometry of mostly Lucy mission targets (with an MPC observatory code Q56) and Jupiter satellite events.

Hristo Pavlov next presented the Occult Watcher (OW) Cloud. The basic Occult Watcher program notifies observers which events are generally near to them. It also allows you to post your expected path position for an upcoming event so that other observers don't duplicate your position. The need for OW cloud comes as the result of the large Gaia catalog, the huge # of events predicted worldwide and the # of parameters associated with each event. One can search by object such as numbered asteroid, comets, interstellar objects, planetary satellites and event date to within the next 2 months. As an example, Hristo chose asteroid 2207 Antenor for July 30, 2021 and the program searched over 20 million stars and within a few seconds, 10 events were output. Certain events may be "tagged" such as the need for observations (such as the recent Moon discoverd around 4337 Arecibo) or an asteroid with a few or no observations. The program can bring up a Google map of your intended location, a DSS image of the star field and predicted error margin ellipses.

 

Peter Nosworthy presented the observations leading up to the discovery of a satellite of the asteroid 4337 Arecibo. Dave Gault and Peter Nosworthy reported to CBAT the discovery from the occultation of the star UCAC4 323-126197 on 2021 May 19.74861. The observers were separated by 0.7 km across the occultation path, and 18 km along the path. Both observations were made using GPS time-stamped video. Peter played the 4 videos from the observers (his video, Dave Gault, Kirk Bender, and Richard Nolthenius) of Arecibo showing the double disappearence of the target star.

 

The light curves from all 4 observers are shown below:

 

 

 

 

Both observers recorded two occultation events with the following characteristics.


Observer
........................Location .................................Chord Lengths
.....................................(Australia) ........................Main body ...........Satellite
D Gault
.................Hawkesbury Heights ....................18.7 km ..........5.6 km
P Nosworthy
...............Hazelbrook ............................19.7 km ..........2.6 km



Just 3 weeks later after Nosworthy and Gault's observation, Richard Nolthenius and Kirk Bender report the confirmation of the satellite (from California) from the occultation of the star UCAC4 322-116848 on 2021 June 9.45736. The observers were separated by 8.2 km across the occultation path, and 8 km along the path. Both observations were made using GPS time-stamped video. Both observers recorded two occultation events with the following characteristics.

Observer
......................Location ..................................Chord Lengths
...................................(California) .......................Main body ............Satellite
R Nolthenius
..............San Ardo .............................23.9 km .............11.7 km
K Bender
.....................Bradley ..............................20.8 km .............13.0 km

 

 

 

The sizes of both the main body and the satellite were poorly determined by the first occultation, because of the close across-path separation of the observers. The sizes of both bodies were well determined from the second occultation, because the across-path separation was larger, and the chords were favourably positioned against both bodies. On the assumption that the bodies presented a circular profile, the diameters determined from the second occultation are:

 

Main body 24.3 0.6 km
Satellite
....13.0 1.5 km

These diameters were used to derive the position of the satellite relative to the main body, for both occultations. Those positions are:

2021 May 19.74861 25.5 1.0 mas in PA 105.2 1.0
2021 June 9.45736 32.8 0.7
.mas in .PA 94.3 2.7


Dr. Richard Nolthenius presented follow up observations of the (4337) Arecibo occultation on June 30th across California and the preliminary orbital constraint estimates for the Arecibo satellite. Richard first described how he chose sites for Kirk Bender and himself, with potential wind-shake of video records as primary determiner for Kirk Bender who was without a car to help as a wind shield. He showed successful light curves from his 3 person team, including CSU Professor Chris Kitting. All showed no evidence of the satellite. He showed the sky plane plot of the satellite's changed position between the Gault/Nosworthy May 19 discovery to the Nolthenius/Bender June 9 confirmation 20.7 days later. He showed an estimate of the smallest reasonable semi-major axis a, about 100 km (giving a period of ~2.5 days), and also the largest possible of a=293 km, set by Jupiter's tidal pull, assuming a representative mean density of 1.9 g/cm3. He showed a 20 day period most simply suggested by the earlier data, is impossible as it puts the satellite beyond the Jupiter tidal limit. Instead, periods of 10, 5, or 2.5 days are more likely. Even these assume the May 19 and June 9 observations saw the satellite on the same side of the sky plane, which is has a 50% chance of being correct. Finally, he suggested the best way to determine the period and finalize the orbit is to search photometric data from PANSTARRs and/or SuperWASP for a photometric period, as tidal locking is likely to ensure this period is also the satellite orbital period. Then, matching with the two satellite-observed occultation observation dates would fix the orbit and allow accurate placement of future occultation observers.

 

From both occultations is the combined sky plane profile of Arecibo and its satellite

 

 

Dr. David Dunham talked about some unusual asteroid occultations. He first mentioned 234 Barbara observed at IOTA's meeting in 2009 in Florida and that its strange lobed shape warranted further observations. He showed sky plane plots of other asteroids observed with satellites and strange shapes:

2258 Viipuri in Aug 3, 2013 and Sep 19, 2018 (each of these occultations had a secondary occ'n, probably by the same moon of Viipiri)
(9634) 1997 WP21 on Feb 14, 2021 (NEW satellite)
479 Caprera Mar 28, 2020 the prediction wasn't good. He, Joan and Ted Blank set up several stations, Ted got 2 chords.
513 Centesima Dec 20, 2020. unusual shape, maybe like Barbara
Ganymede Dec 21, 2020
1224 Fantasia Feb 21, 2021 - was good practice for Apophis the following month
8 Flora Mar 18, 2021, very close double star
(14758) 6519 P-L May 29, 2021 Main belt (not Trojan), peanut shaped asteroid with a bulge on the far east side.
4337 Arecibo June 30 2021. 4 stations, resources spread too thin, and all failed to get data.
477 Aguntina July 12, 2021, A rank 100 event, a large asteroid, no positives and 2 misses made by Steve Messner and Henry Throop.

David next spoke about NEO occultations starting with the 2300 Phaethon event from July 29, 2019. He showed observer stations and the resulting sky plane profile that resulted in 6 positive chords.

The success of this Pahethon event allowed an update to the orbit to prepare for the Sep 29, 2019 event and future events. In Oct 5, 2020 - Roger Venable made a successful observations of Phaethon further refining it's orbit. David then showed some future Phaethon events include Sep 22, 2021 across the eastern USA.

For the Apophis occultation on Mar 7, 2021, stations were set up at 107m intervals at a private airport in Louisiana due to its small size. 3 positive events were obtained: Dunhams (2) and R. Nugent (1). The next Apophis event was March 22, 2021, and Roger Venable set up 5 stations and his most eastern station had the only positive chord.

For the next Apophis occultation prediction on April 4th, he suggested down-weighting the position of the asteroid/star position from the Mar 7th event. This was due to the fact that the star occulted on March 7 was an eclipsing binary. This meant that the position of the occulted primary (brighter) star was moving at a non-uniform rate altering its position and motion from the gravitational influence of the 2nd star.

The Apophis event April 4, 2021 and 3 positive chords were obtained - 1 each by by Roger Venable (he also had 4 negatives, valuable for constraining the path) Kai Getrost and 1 by N. Carlson.

Apophis May 6, 2021: 5 successful observations in a north-south path over northwestern Mexico and southwestern USA. One of the successful positive observers was Hermosillo Sonora. These latest observations further refined Apophis's orbit. Future events include September 5, 2021 over the Middle East and Sep 27, 2021 over the Georgia coast with only an 8 deg altitude!

 

Dave Herald presented the observed events of last year worldwide.

2020 - Nearly 900 events/year observed and growing. In 2019, just under 600 events were observed. The unusable events have been dropping also, with only 3% of 2020 events still under scrutiny.

Events by location:

Australasia 157
Europe 316
Japan 66
N. America 316
S. America 21

Most of 2020 (876 observations) were single chord observations, 2-3 chords=250 events, 4-9 chords=80 events, 10+chords = 10 events. Other statistics Dave showed were the # of observers per event, which has been on the decline in the past 10 years, # of successful events by region and double star discoveries. Double star discoveries have separations in the range of 10-100 milli-arcseconds.

Binary satellites - 2 discoveries sor far in 2021 - 1997 WP21 and Arecibo. With the estimated number of satellites asteroids should have, the first 5000 asteroids have 118 satellites discovered = 2.3%. In 2020 we observed 876 sevents, this should amount to 20 asteroid satellites. But in 2020 we observed just 2 satellites, only 0.2% of all events! Dave questioned whether or not we are interpreting these observations correctly. One theory is that if the recording doesn't include stars more than 1 mag fainter that the target star, you cannot reliably distinguish between a double star and a satellite.

Dave mentioned another issue with some observations - not every chord matches the expected profile. He showed a few asteroid profiles illustating this. He stressed the need for accurate times taking into account camera delays and recording delays from different recorders (DVRs, computers). A time base shift could also be an issue.


Dave Herald then discussed the evolution of astrometry from asteroid occultations. The first astrometric position reported from an asteroid occultation was in 2008. The Minor Planet Center has assigned for occultation derived positions Observatory Code 244.

The intial problems with determining astrometric positions was the math used and the exact time of conjuction of the star and asteroid. Another such issue is the gravitational deflection caused by the Sun - it is different for the star and asteroid. Another issues is whether to use Sun centered or Earth centered coordinates. He decided the solution was to report the (x,y,z) coordinates of the asteroid's shadow at the location in the center of the Earth. Dave showed a sample MPC report showing the observer names, time of central occultation, residual RA and Dec and other parameters. The typical astrometric accuacy from occultations are 1-10 mas which is is 10-100X better than the typical astrometric position obtained using other methods such as ground based telescopes. As a result, occultation positional accuracies are highly sought by the MPC and JPL Horizons.

 

 

------------------------- July 18 20:00 UT Meeting begins. Online attendees reached 74 persons------------------------------

Aart Olsen started the day with a talk about the GPS + Ardunio LED flasher. This simple device makes precisly timed flashes that are recorded on an occultation video. Its a useful device since phones, computers, WWV or internet aren't needed, just a GPS signal. Aart showed images of this device and how it powered. It can use a USB power input or the 12v power that are used for our cameras.

Users will need only minimal assembly of the device -- soldering a few wires. The Arduino Integrated Development Environment (IDE), the program that lets you write the code and program the Arduino, is available at https://www.arduino.cc/en/software and Aart's flasher code can be copied from https://groups.io/g/IOTAoccultations/files/Aart%27s%20Arduino%20Timers/Led%20SD.txt and pasted into the IDE.

He showed the steps needed to program and load the code into the device. Once the code is loaded, it will remain and not be erased even if the device is turned off, or put away from long periods. Once turned on, the LED flasher will flash at the intervals the user previously specified into a file Input.txt in an SD card.

The precise flashes are seen as spikes in the background of the video which is seen by PyOTE and PyMovie. Aart showed an example light curve showing the flashes from an occultation John Moore observed in 2020.

Flashes (red spikes) on occultation by John Moore

 

Aart Olsen then spoke on a "Simple Exposure Time Analyzer." Aart showed how to make a device similar in function to the established EXTA and SEXTA camera analyzers using the same Arduino-GPS timer as the LED flasher, plus some inexpensive LED displays easily found on ebay or Amazon.  The MIDWEXTA   (Aart says you don't have to call it that if you don't want to), shows UTC, with subseconds displayed as a rapidly moving dot on the 512 LED matrix.  The code used to program the Arduino using the IDE can be copied from here:

https://groups.io/g/IOTAoccultations/files/Aart%27s%20Arduino%20Timers/Camera%20analyzer.txt

The device outputs digital UT times, # of GPS satellites. It's coded just like the Arduino flasher. He showed several video frames comparing the IOTA VTI GPS times vs. the time analyzer. The comparison times from both devices were in excellent agreement. See image below.

 

Richard Nugent presented a program available as a cell phone app to predict Baily's beads during solar eclipses. The program "Eclipse Calculator 2" is a free download from the Google Play Store for Android phones. Written by Eduard Basana from the University of Barcelona, the program features predictions and data for solar and lunar eclipses plus planetary transits from the years 1900 - 2100, expandable to years 1550 to 2300. Some of the many features of this program include start and end times for any eclipse for 100's of locations/cities in every country (including user created locations), altitudes, azimuths, delta T values (along with estimates for future eclipses), Google style maps for each eclipse, path and shadow simulations, plus a lunar limb Baily's beads feature. Richard has been in contact with the author and suggested modifications of the app for IOTA purposes which the author implemented.

 

For any eclipse, you can tap on the Google style map and a pop-up window appears displaying eclipse circumstances for that location. The Baily's beads feature allows the user to move their finger on a sliding bar and watch how the beads appear, grow and disappear with Universal Times displyed to the nearest tenth of a second. Nugent showed screen shots of Baily's beads videos he and the Dunhams' have obtanied compared to the app. The results Eclipse Calculator 2 displayed were in excellent agreement with the actual videos.

 

Shown below are Eclipse Calculator 2 Baily's beads screen shots and comparison to the August 1, 2008 eclipse actual video frame by Richard Nugent plus Joan and David Dunham's Baily's beads video frame from the July 2, 2019 eclipse in Argentina.

 

 

 

 

 

 

 

 

 

 

 

 

Bob Anderson talked about how he has added diffraction modeling in PyOTE. Diffraction fringes between the star and asteroid during an occultation can sometimes cause a false D and R, so hence the need for diffraction model in the light curve reduction program. Bob wrote the modification based on research from Raymond Dusser, Michael Richmond and Seymour Trestor. Bob showed an image of the classical diffraction pattern curve from an occultation. Bob then showed the expected diffraction pattern for an 8km sized asteroid, with a distance of 2.57 AU. The fresnel length came to 0.311 km. He then showed the fresnel unit diagrams for a 930km asteroid at the same distance. Bob's tests showed that there's an insignificant difference between a single wavelength diffraction curve vs. one with a passband with multiple wavelengths. With diffraction implemented in PyOTE, one can use this tool to rule out a possible short blink from a satellite compared to a diffraction fringe effect. Dave Herald mentioned that the star diameter if known in advance should be taken into account.



Kevin Green spoke about electronic line noise in our videos. Line noise produces non-uniformity in the background between video frames and between reference stars and the target. Kevin showed how to elminate the line noise and showed a video frame showing the result. When removing the line noise, the signal to noise S/N increases. For high S/N events, line noise is not affected, for low S/N events, it could mean detection vs non-detection of a D or R event.

Line noise removed from video.

 

Kevin next discussed D & R timing when there are dropped frames. He used the example of the occultation by 940 Kordula from 19-Oct-2020. The telescope used was a Celestron 14Edge SCT. Although the light curve looked good, zooming in showed some dropped frames unfortunately near the D and R times. Kevin estimated that 8.9% of the frames were dropped in the video. To help solve the problem, Kevin showed an example using a Monte Carlo simulation to show where the D and R times likely should be.

With the Kordula event, the D and R times and error estimates were:

D = 4:42:06.33 +0.33/-0.35
R = 4:42:38:315 +0.14/-0.66

Tangra gave times differing by 0.4 sec which was lower than PyOTE for this event. Kevin concluded that dropped frames aren't fatal as they can be quantified.


Atila Poro from IOTA's Middle Eastern Section presented a value of Pluto's atmospheric pressure based upon 2020 stellar occultation light curve results. The Pluto event observed by the IOTA Middle Eastern section was on June 6, 2020. The star magnituide was +12.97. The data was used to obtain the atmospheric pressure of Pluto. The observation was made at a private observatory north of Karaj City, Iran. The main telescope used was a 24" SCT, 2nd scope used a 14" SCT. Two identical SBIG CCD 1100M cameras were used on both telescopes.

 

Light curve of Pluto occultation: 2020 June 6

 

234 images were taken simultaneouly with both cameras with 24 usable images from the occultation. From the light curve he determined the Pluto's atmosphereic pressure 6.72 +/- 0.21 ubars in reasonably good agreement with past stellar occultations.

Altila and his colleagues published a paper on their results. It is available at
https://arxiv.org/abs/2011.04737



Atharva Pathak gave an overview on IOTA-India's activities. This IOTA section was born on May 3, 2019. Members observe lunar and asteroid occultations, variable stars, meteor showers as part of India's oldest amateur astronomy club: Jyotirvidya Parisanstha (JVP). Their website
http://iota-india.in/ includes:

Observing Basics (what is an occultation, and how to observe it)
Occultation Predictions
Occultation Observational data
Educational Materials
Software
Recommended equipment
Reporting Observations

IOTA-India also has a facebook page:
https://www.facebook.com/groups/OccultationObservers

Their You Tube Channel:
https://www.youtube.com/channel/UCiTT_evtRe39LK5tmP6URuA

Their website also encourages engaging with the public to recruit new observers. Regarding timing, Atharva mentioned that ordering the IOTA-VTI is expensive for their budget in addition to the mailing costs involved which could run $60 USA and higher.
Atharva introduced a new Android App developed SAT TIMER, which was developed as the Time Sat app doesn't work on some android versions.

Their future plans include developing low cost setups, plan training sessions across the country for reporting lunar and asteroid occulatations, engaging in outreach activities for popularizing occultations, designing University level projects for occultation observation and analysis and explore new apps and web tools.




David Dunham spoke on rethinking the RASC (Royal Astronomical Society of Canada) handbook's occultation section. He gave some ideas he has for updating the 2022 handbook. The current handbook, has 17 pages for lunar occultations which includes graze maps for North America with tables, 5 pages for asteroid/planetary occultations. David proposed for 2022 lunar occultations - 14 pages, asteroid/planetary - 8 pages.

David showed the history of the handbooks occultation predictions:,
1988 - ILOC-Japan did the lunar events, planetaries by BNob Millis (Lowel Obs), E. Riedel and David did the graze section

1990 Larry Wasserman took over planetary predicitions from Bob Millis

1992 - graze section credited to Dunham,

1999 - E. Reidel added explicity as main author of grazes,

2000 - Planetary Occultation section done solely by IOTA

2003 - Lunar occultations section solely by IOTA, Dave Herald and David Dunham credited as authors of the total occultation section.

The new layout will keep the introductory pages, ZC star names, double star list and total occultations. Total occultations will have bright stars with the list more compact. There will be only 1 graze map and 1 table for bright stars only. Other lunar graze maps will be on the web. The 3 pages of tables and notes for asteroid events will be replaced with maps of different classes of events: Main-Belt asteroids, Trojans, TNO's and Centaurs with tables and explanations of each.



Filipp Romanov
provided information on occultations of stars and planets he has observed from Russia. Filipp is 24 years old, and has limited resources. He has discovered (by self-education) 74 variable stars, 10 planetary nebula candidates, and other objects, he is an author of two scientific papers in astronomy published in journals. He made his first presentation ever to the AAVSO 109th Annual Meeting on November 13, 2020 on one of his eclipsing binary discoveries: Romanov V20. He talked about his observing history of occultations from his first lunar occultation on March 29/30, 2012 and then the Venus occultation in August 2012. For the first time he attempted to observe the (1107) Lictoria asteroid event from Primorsky Krai (from his small homeland, on the Far East of Russia) on December 27/28, 2012 of Theta1 Tauri.

In Moscow, he observed by video of end of occultation of HD 95848 (mag = 7.2 star) by Jupiter on April 12, 2016; lunar occultation of Neptune in June 2016; daytime occultation of Aldebaran on August 16, 2017 and he showed the star visible in photos.

On September 1, 2016, in the capital of Russia, he observed the asteroid event of 159 Aemilia occulting TYC 6349-00855-1. He used a Canon EOS 60D camera attached to a telescope. He used a time exposure to catch the event (see the star missing in the time exposure) and obtained a >7.5 sec occultation (only reappearance: disappearance happened during 4-sec interruption between photos).




He also observed the occultations of Aldebaran in Moscow Oblast: in April and August 2015 (in science city Korolyov) and in February 2018 (in science city Protvino) - by video with his DSLR camera and 135mm telephoto lens.

Due to housing trouble in a communal apartment in Moscow, from 2017 to present Filipp has had to travel in wanderings around regions of Russia. His goal is to attend a university and study astronomy. You can contact Filipp by email filipp.romanov.27.04.1997 at g - mail. Filipp also has pages on Facebook, Twitter, Instagram, Flickr and a Youtube channel, where the descriptions for some videos contain details of his difficult life situation.

His webpage (mostly Russian but can be translated) is: https://filipp-romanov.livejournal.com/



Roxanne Kamin spoke on the challenges of introducing new observers to occultations. Some of the best location site candidates for occultations are fixed site observatories managed by local clubs and universities. Typical challenges include scheduling practice sessions, recruiting volunteers on a weeknight and working with equipment limitations due to budget cuts and COVID restrictions. Other issues include out of pocket start up costs (e.g. camera, IOTA-VTI, and cables) with an $800-$1500 outlay being the typical cost to get started.

New observers note that not all of the cameras listed are currently available and if all of the software noted on IOTA's website is required. In addition, IOTA's reliance on WIN based software (update sensitive) was also a concern with the use of specialized cameras (e.g. mono video) vs the use of more popular MallinCam and ZWO ASI Air systems was also a deterrent. Our documentation noting the use of visual timing, VCRS and outdated technology can be overwhelming and confusing to apply occultation efforts and camera use.

Roxanne encouraged the use of local observatories to employ public outreach, offer networking within the scientific community, participation in citizen science and the potential for publication (e.g. newsletters, web articles, academic papers). Noting that having one's name published for an occultation observation may assist in providing additional funds for the observatory and encourage recruitment of new long-term observers and future IOTA contributors.



Dr. Joan Dunham next talked about citizen science opportunities for IOTA. The idea is to give ideas during presentations and talks to astronomy clubs and enthusiasts. Joan has recently made a citizen science page on the IOTA website:
https://occultations.org/campaigns/

IOTA members provide predictions, coordinate observations, provide software, report and publish observations and teach others techniques, how to observe and how to utilize the software.

Joan suggested encouraging people to observe without requiring IOTA membership, provide examples of recent successes such as 3200 Phaethon and 99942 Apophis (whose possible danger to the Earth was dismissed following radar and occultation observations), make predictions available for bright stars and interesting events local to the area and the websites for occultation information. Any talk should have an equipment demo - people respond better when they see the actual equipment (small telescope, camera, recoder, IOTA VTI) vs. just photos on a PowerPoint. Joan also mentioned its a good idea after a talk to leave flyers and lists of the next visible occultations event for the area.



Joan then discussed a Boot Camp Proposal for Occultation Observers. A bootcamp can include a daytime session for using software, an evening session on equipment use, and even a session for high profile events (SwRI, Lucky Star).

Observing sessions can include: observe when the Moon is near dense star fields, IOTA annual meeting events. Software sessions can be done in person, via Zoom, anytime anywhere. Participants should have a telescope, camera, and a way to record the data - visual observations are discouraged. Joan listed items to be covered: sessions before observing, practice session and data reduction sessions. Sessions can also be during a member or public star party.

 

 

 

The Meeting adjourned at 00:40 UT, July 19

                                

                                The minutes of all IOTA's annual meetings are at: http://www.poyntsource.com/Richard/IOTA_Annual_Meetings.htm

 

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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.