th

August 2 – 14, we returned to the USA, but only to Honolulu, Hawaii, to attend the 29 th General Assembly (GA) of the International
Astronomical Union (IAU). IAU GA’s take place every three years and last for two five-day sessions spread over two weeks. Previously, I attended IAU GA’s in 1967 (Prague, Czechoslovakia), 1970 (Brighton,
UK), 1976 (Grenoble, France), 1979 (Montreal, Quebec), 1982 (Patras,
Greece), and 1988 (Baltimore, Maryland).
They provide a unique opportunity for astronomers worldwide working in all fields of astronomy to come together. In addition to the core administrative meetings, the General Assembly also includes a substantial and attractive scientific program. This usually comprises two series of three Symposia each lasting for three days, and scheduled during the first and second weeks, respectively. Fifteen to twenty more specialized "Focus Meetings" are also held, with up to five topics running in parallel. In addition, two full days are reserved for Division
Meetings, with no overlap with the general program.

Symposia of the 29 th IAU GA included:
•IAUS 315 – From Interstellar Clouds to Star-forming Galaxies: Universal
Processes?
•IAUS 316 – Formation, Evolution, and Survival of Massive Star Clusters
•IAUS 317 – The General Assembly of Galaxy Halos: Structure, Origin and
Evolution
•IAUS 318 – Asteroids: New Observations, New Models
•IAUS 319 – Galaxies at High Redshift and Their Evolution Over Cosmic
Time
•IAUS 320 – Solar and Stellar Flares and Their Effects on Planets
A special session described first results from Gaia (first year obs.)
Symposia programs & other IAU details are at http://astronomy2015.org/science_program

Focus Meetings of the 29 th IAU GA included:
•FM 1 – Dynamical Problems in Extrasolar Planets Science
•FM 2 – Astronomical Heritage: Progressing the UNESCO–IAU Initiative
•FM 3 – Scholarly Publication in Astronomy: Evolution or Revolution?
•FM 4 – Planetary Nebulae as Probes of Galactic Structure and Evolution
•FM 5 – The Legacy of Planck
•FM 6 – X-ray Surveys of the Hot and Energetic Cosmos
•FM 7 – Stellar Physics in Galaxies Throughout the Universe
•FM 8 – Statistics and Exoplanets
•FM 9 – Highlights in the Exploration of Small Worlds (results from Rosetta, Dawn, New Horizons)
•FM 10 – Stellar Explosions in an Ever-Changing Environment
•FM 11 – Global Coordination of Ground and Space Astrophysics and Heliophysics
•FM 12 – Bridging Laboratory Astrophysics and Astronomy
•FM 13 – Brightness Variations of the Sun and Sun-like Stars
•FM 14 – The Gravitational Wave Symphony of Structure Formation
•FM 15 – Search for Water and Life's Building Blocks in the Universe
•FM 16 – Stellar Behemoths - Red Supergiants Across the Local Universe
•FM 17 – Advances in Stellar Physics from Asteroseismology
•FM 18 – Scale-free Processes in the Universe
•FM 19 – Communicating Astronomy with the Public in the Big Data Era
•FM 20 – Astronomy for Development
•FM 21 – Mitigating Threats of Light Pollution & Radio Frequency Interference
•FM 22 – The Frontier Fields: Transforming our Understanding of Cluster and Galaxy Evolution

On behalf of IOTA, I gave four poster presentations, all during the first week:
1. Results from Asteroidal Occultations (Josef Durech was there)
2. Double star results from occultations
3. Solar diameter results from total and annular solar eclipses
4. Plans for the 2017 August 21 st total solar eclipse
In the following, I give at least the title slide of each; the full posters (Power Point files) will be given in a subfolder in the
IOTA meeting presentations section

David W. Dunham*, David Herald, Steve Preston,
Bradley Timerson, & Paul Maley, International Occultation
Timing Association (IOTA); Eric Frappa, IMCCE, Paris; Tsutomu
Hayamizu, Japanese Occultation Information Network; John Talbot,
RASNZ Occ’n Section; and Atila Poro, IOTA/Middle East Section, Iran
* Email dunham@starpower.net Cell phone 301-526-5590
International Astronomical Union - General Assembly Honolulu,
Hawaii, 2015 August 3 – 7 - Control ID 2258262
For 40 years, the sizes and shapes of dozens of asteroids have been determined from observations of asteroidal occultations. Some of the first evidence for satellites of asteroids was obtained from the early efforts; now, the orbits and sizes of some satellites discovered by other means have been refined from occultation observations. Also, several close binary stars have been discovered, and the angular diameters of some stars have been measured from analysis of these observations. The International Occultation
Timing Association (IOTA) coordinates this activity worldwide, from predicting and publicizing the events, to accurately timing the occultations from as many stations as possible, and publishing and archiving the observations.

Used by observers to find potential occultations that they can observe, filtered by distance (larger distances for mobile observers), star mag., etc., and give event details, including links to star charts, etc. Through a Web interface, mobile observers can then set up to fill gaps in coverage by those at fixed observatories.

Lightcurve from Dunham Station #3 for 2011 Dec. 28th occ’n of
SAO 138052 = HIP 54719 by (407) Arachne e. of Huntsville, TX
Video analyzed by Scotty Degenhardt. The site was a graze near the n. limit; the star disappeared completely behind 3 features on the edge of the asteroid.

Still the record, Scotty observed from 14 stations in Oklahoma
!
Scotty & I agreed before that I would cover the n. side & he the s. side, so each of us could deploy more stations across a shorter distance. This time, the path shifted s. so he hit the jackpot. 3 LA region fixed observers expected no event, but ended up defining the southern part of Hertha.

2011 July 19 occultation of LQ Aquarii by the binary asteroid (90) Antiope observed in western USA
Above is the best direct image of
Antiope, by
Bill Merline using AO with Keck
3d before the occultation; it allowed a good prediction of the objects’ orientation.

Sky-plane plot, 2012 Jan. 19 th
(911) Agamemnon occultation
Below:
Light curve by Steve Conard (sta. 6) using a 14-in. SCT at his observatory at Gamber, Maryland
Above:
Agamemnon: Axes 190.6

0.9 by
143.8

1.5 km, PA minor axis -69.3


1.3

, center X 4661.6

0.4 km, Y
3113.7

0.6 km; Disappearances are on the right side. The probable satellite is plotted as 9-km circle (but it’s more likely about 4 km across)
0.0931

(278 km in the plane) from
Agamemnon’s center in PA 93.8


The RASC Observer’s Handbook contains predictions of the 
70 best asteroidal occultations visible from North America and Hawaii during the year.
Many occultation YouTube videos are linked to from: http://www.asteroidoccultation.com/observations/YouTubeVideos.htm
Listed on this web page are, in groups from top to bottom,
Lunar Occultation Videos; Asteroidal Occultation Videos; Jupiter/Saturn Satellite Events
Miscellaneous Events (most of them are solar eclipse videos made near the edges of total and annular solar eclipse paths)

David W. Dunham, Anthony George,
Brian Loader, and David Herald,
International Occultation Timing Association (IOTA) and high-speed CCD observations by Andrea Richichi, National Astronomical
Research Institute of Thailand
International Astronomical Union - General Assembly
Honolulu, Hawaii, 2015 August 3 – 7
Control ID 2256339

• Duplicity of Antares discovered during a lunar occultation observed at Vienna by Johann Tobias Bürg on 1819 April 13. I observed a graze of Antares by the thin crescent Moon on 1969
January 25
• Contrast of the red giant star and its 5 th -mag. blue companion was striking
• I recorded an Antares graze with a color video camera and 12cm
SCT from Western Australia on 2009 Feb. 17
• Show events of both components, 19:44:10 to 19:44:25 and
• 19:47:00 to 19:47:30

Reduction profile by Dr. Mitsuru Sôma at the National
Observatory, Japan. The lunar mean limb is the horizontal line at 0
 and heights are in units of
 at the Moon’s mean distance
(1
 then is 1.86 km). “Axis Angle” is position angle measured relative to the Moon’s axis of rotation.
For each observer (and each stellar component), the star follows a parabolic arc.
Cloud interference, esp. near the end, resulted in some spurious events. Kaguya & LRO laser altimeter profiles are very accurate.

• In the early 1970’s , I worked with David Evans’ group at the Univ. of Texas to analyze hundreds of photoelectric lunar occultation observations
• I worked with a student, Don Stockbauer, to create a list of possible doubles from lunar occultations using:
- Photoelectric occultations, Univ. of Texas and other published obs.
- Grazing occultations observed since 1962
- Total occultations, both current and from published obs.
Spectroscopic binaries (including 1-line) were included to encourage observation of their occultations.
• Too many dubious events were included; especially visual observers often reported “gradual” events more likely due to Fresnel diffraction , and sometimes stellar angular diameter
• Codes that indicated “certain, events in clear steps”, “probable”, and
“possible” were lost when transferred to currently-used lists , for occultation predictions but also even the Washington interferometric catalog

• We now strongly encourage observation with relatively inexpensive video equipment to better quantify the observations, and obtain at least approximate photometric information using specially-developed software for analyzing video records, esp.
Limovie from Japan and Tangra from Australia
• We encourage observation of stars with a past claim of duplicity ;
•
Over 90% of those show no evidence of duplicity with the new video obs.
• We encourage observations of the same occultation of a suspected double from widelyseparated locations with real-time coordination using “Occult Watcher” Web software.
• If the same lunar occultation is observed from widely-separated locations (with the contacts at different position angles), the separation and position angle (P.A.) can be uniquely determined ; otherwise,
• Only a “vector separation” in the P.A. of the occultation is found
• If orbital motion slow, “vector separations” from events a few months apart can give approximate double star separation and P.A.
• Results are published in JDSO periodically, including lists where the new observations indicate “probably single” for previous occ’n duplicity claims
• We have begun a collaboration with the current Kepler2 ecliptic program, to obtain (or find past) occultation lightcurves of their program stars, to help assess close stellar duplicity that might affect Kepler’s analysis for exoplanet transits. We are starting to collect and archive new and past occultation lightcurves.

Multiple events of 2 close components from a video recording of a lunar grazing occultation observed in Australia

X63280,
2014 Dec 31
23

• Is mainly coordinated now by
Andrea Richichi at the National
Astronomical Research Institute of Thailand, andrea@narit.or.th
• He worked before for a long time at the
European Southern
Observatory, where he still makes most of his observations
• Most observations are recorded in the infrared, allowing higher
S/N and even some daytime observations
• Observations are concentrated on times when the Moon traverses the Galactic center region , an area of obvious high interest; a hundred occultations might be recorded in a single night
• Passages over the Pleiades and other interesting clusters are also observed
• The equipment is set up so that it can be used during “dead times” between other astronomical observations

Instruments & Detectors

Photometers, photomultipliers, InSb diodes

APD, SPAD

CCD (drift scanning)

NIR Arrays (subwindow)

Specialized small format arrays (AO)
2.4m f/10 TNT, alt. 2400m since Mar. 2012

Lightcurve of occultation of SAO 80827 by (160) Una recorded by Dennis DiCicco at his observatory in
Sudbury, Mass., 2011 January 24
Video at http://www.asteroidoccultation.com/observations/YouTubeVideos.htm

David W. Dunham*, Internat’l Occultation Timing
Assoc. (IOTA); Sabatino Sofia, Yale Univ. – retired;
Konrad Guhl, IOTA/European Section; and David Herald, IOTA
* Email dunham@starpower.net Cell phone 301-526-5590
International Astronomical Union - General Assembly Honolulu,
Hawaii, 2015 August 3 – 7 - Control ID 2257941
Since thermal relaxation times for the Sun are thousands of years, small variations of the Solar intensity are proportional to small variations of the Solar diameter on decadal time scales. In a combination between observations and theory, reliable values of the relation constant W are known, that allow transformation of historical variations of radius into variations of the solar luminosity. During the past 45 years, members of the International Occultation Timing Association (IOTA) have observed
20 annular and total solar eclipses from locations near the path edges. Baily’s beads, whose occurrence and duration are considerably prolonged as seen from path edge locations, were first timed visually, mostly using projection techniques.

• IOTA’s long term solar radius measurement research
• Observations near central eclipse path edges since 1970
• Analysis of historical obs. back to 1715; look for more
• Re-analyze all obs. with accurate profile data- eg, LRO
• These large tasks manageable with some help from others in and outside of IOTA

Solar Radius Determinations from Solar Eclipses
The radius correction, delta-R, is relative to the standard value at 1 A.U., 959.63 arc seconds.
All have been reduced using David Herald’s WinOccult program and analyzed with the Solrad programs. The Delta-R values are from 2-parameter solutions using bead events within 30 ° of the poles to use the better accuracy of the lunar polar profile as explained in a previous slide.
30

• Search publications and local university archives for past observations to analyze
• Work remains to be done, for example, on the rather wellobserved US eclipses of 1806 and 1869
• The Internet facilitates connection with local historians who can often find information about past observations.
• Google Earth and other GIS tools make position determination much easier than using topo maps
• Re-analyze all obs. with accurate profile data- eg, LRO
• New observations with previous and modern techniques, especially at the 2017 eclipse, are needed to calibrate the earlier observations
• Anyone near a university or a central eclipse path, or even with just internet access, can help

David W. Dunham* and Richard Nugent, International Occultation
Timing Association (IOTA); Konrad Guhl and Hans-Joachim
Bode, IOTA/European Section
* Email dunham@starpower.net Cell phone 301-526-5590
International Astronomical Union - General Assembly Honolulu,
Hawaii, 2015 August 3 – 7 - Control ID 2258483
The August 21 st , 2017 solar eclipse provides a good opportunity, to time the totality contacts, other Baily’s bead phenomena, and observe other dynamic edge phenomena, from locations near the edges of the path of totality. A good network of roads and generally favorable weather prospects means that more observers will likely be able to deploy more equipment than during most previous eclipses. The value of contact and Baily’s bead timings of total solar eclipses, for determining solar diameter and intensity variations, was described in an earlier presentation in
Focus Meeting 13. This poster will concentrate on how observations of different types that have been used during past eclipses can be made by different observers,

Unique opportunity to deploy greater resources than usual

• Continuation for IOTA’s long term solar radius measurement research
• Standardization of video equipment
• Standardization of solar filters
• Co-located use of previous techniques (visual, telescopic projected image, filtered telescopic video)
• 2nd use of narrow band filters (1 st was for the May 20,
2012 annular eclipse)
• Desired Results: calibrate with Picard satellite data and with methods used at previous central eclipses

• Telescope aperture: 75mm – 100mm
• Field of View – 15
' - 20 '
• Solar filter – Baader brand – in sheets
• Narrow band filters – Wratten #23, #56
• Attempt to observe in Picard wavelengths
• Video camera: PC164C(EX-2), Watec
902H

Ted Swift, S. Limit of May 2012
Annular Eclipse 15 sec interval
Unfortunately, clouds prevented observation near the northern limit.

January 24, 1925 Total Solar Eclipse – Boy Scouts and Con Ed workers found the southern limit by observing at one-block intervals across Manhattan. Similar efforts might be made at towns straddling the limits of the August 2017 TSE, a public outreach opportunity

• Aug. 5, grazing occultation of 6.5-mag. 96
Piscium across southern Honolulu with path only a mile south of our hotel (first graze where we walked to the graze zone). We brought a
120mm maxi and due to the 73
 altitude, we brought & used a paver mount. John Broughton plans to make lighter versions of those for better air transport.
• Aug. 13, possible occultation of 9.6-mag. star by
(1197) Rhodesia – I thank Ernie Iverson for the pre-point charts for this & all AU events

August 5, 4:25am HST, graze of 6.5-mag. 96 Piscium 7
 from northern cusp of 67% sunlit Moon, altitude 73


Possible Oahu occultation of 9.6-mag. PPM 171360 by (1197)
Rhodesia predicted on 2015 August 13 at 7:53 pm HST
The target star is in northern Aquarius at J2000
RA 21h 09m 46.2s
Dec +01
 07’ 18”
Predicted size of (1197) is 49 km. The expected central Duration is 3.3s with a 5-mag. drop. The
Predicted altitude is 24
 in the east.
More about this event will be posted here on Thurs. & Friday. Contact
David Dunham if you might try to observe this. dunham@starpower.net
Cell 301-526-5590

On target, cloud moved over
FOV few seconds after the predicted time, a miss, but
Sherrod’s AR miss (purple) was closer. Bart Billard recorded his first positive at
Fredericksburg, VA with a
CCD drift scan.