The International
Occultation Timing Association's 38th Annual Meeting
July
25-26, 2020 via Zoom online
The 38th annual meeting of the International Occultation
Timing Association was held Saturday and Sunday July 25-26,
2020 via Zoom online. The meeting schedule and agenda are
located on the IOTA web site presentation page:
http://occultations.org/community/meetingsconferences/na/2020-iota-annual-meeting/
Ted Blank has created a YouTube link and uploaded all the
presentations here: https://www.youtube.com/playlist?list=PLY2hxQmBE-LEB9AI-5NESPkPU6Lxkqf_G
Homer F. Daboll Award: Tony Barry David Laird Award: Derald Nye Lifetime Achievement Award: Walt “Rob” Robinson
Attendees: The meeting started out with 68 participants and this number fluctuated to 78 attendees on Saturday and reached 83 participants on Sunday. This is a record for attendence at any IOTA meeting !! A partial list of attendees included President Steve Preston, Vice President Dr. Roger Venable, Executive Secretary Richard Nugent, Dr. David Dunham and Treasurer Dr. Joan Dunham, Jerry Bardecker, John Moore, Bob Jones, Ted Blank, Dave Herald, Jan Kok, Aubrey Brickhouse, Ned Smith, Ted Swift, Suhas Gurjar, Atilo Poro, Tony George, Oliver Kloes, Peter Nosworthy, Roxanne Karmin, Wojtek Burzynski, Rick Bria, Mike Rushton, Aart Olsen, Dave Osper, Bill Hanna, Steve Rottas, Henk Boulder, Hiroyuki Watanabe, Dan Chrisman, Johnny Barton, Alex Knox, Derrick Ward, Steve Messner, Adrian Jones, Esdert Edens, Carles Perello, Bob Jones, Chad Ellington, George Viscome, Kevin Kell, Oliver Kloes, Rick Frankenberger, K. Green, Steve Conard, Jordi Marco, Jan Kok, John Briggs, Tim Haynes, Tom Haugh, Greg Lyzenga, Lawrence Garrett, Jiri Kubanek, Henk Bulder, John Newman, Phil Stuart, Robert Horvat, Maciej Borkowski, Norman Carlson, Russ McCormick, Cal Powell, Julio Spagnotto, Altair Gomes, Terry Redding.
14:10
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.
Treasurer Joan Dunham presented IOTA’s
financials and membership status. In 2019 the Journal of
Occultation Astronomy (JOA) expensive print memberships were
ended since all of those subscribers were email and internet
users. A summary of the year’s income/expense report (September
2019 to July, 2020):
Income:
Expenses:
NET Income: $964.00
*Note:
IOTA has not yet been billed for production expenses for JOA
2020-3
IOTA Balance Sheet
Cash on Hand - Bank and Paypal..........................$12,154.87
MADAMO AWARD...............................................$3,000.00 - Funds dedicated for asteroid moon discovery and confirmation
Reserve Fund - Web Server.....................................$500.00
Future purchase – 3D printer to make adapters for a variety of purposes
IOTA
Membership and Subscription:
Membership only -113
Library
membership - 2
North
American (USA and Canada) members -99
Other
(India, Australian, New Zealand, European) - 6
IOTA Affiliate membership: Joan described IOTA’s new 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.
Executive Secretary Richard Nugent then presented
the 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 Tony
Barry from New South Wales, Australia.
Tony’s contributions to the field of occultation
science are numerous and significant. He became involved in
occultation observing in 2009 after attending a presentation by
Dave Gault at the Western Sydney Amateur Astronomy Group. Tony
soon became aware of the need to develop a low cost but accurate
timing device for use during occultation observations as this
would improve the accuracy of timings and also make high quality
occultation timing more accessible to amateurs. Seeing this need,
Tony has developed two devices to ensure the time-stamp accuracy
of occultation observations:
1. IOTA-VTI - a Video Time Inserter that has
time-stamps with GPS based UTC. The Intellectual Property of the
IOTA-VTI was donated pro-bono to IOTA, who in turn manages the
manufacture and distribution of the device. The IOTA-VTI has
become the standard of occultation timing to observers around the
world. To date, over 300 IOTA-VTI’s have been sold.
2. SEXTA
– Southern EXposure Timing Array is a GPS disciplined device
and analysis App. designed to verify the time-stamps of any
camera imaging system. The design of SEXTA is available Open
Source – available to anyone who needs it, free of charge.
Currently six SEXTAs have been constructed.
In
addition to the IOTA-VTI and SEXTA, Tony has also the lead or
co-author on a number of published papers in the field of
occultation science.
Tony sent
the following message upon his notification of the award:
I am very pleased to accept the Homer F.
Daboll prize for 2020, and appreciate the expression of support
from the community of occultation observers. I would not have
been able to make the IOTA-VTI or SEXTA without the help of Dave
Gault, whose fanatical attention to operational quality made the
VTI and SEXTA work as they ought to. Thank you Dave !
Dave Herald worked the licence details so
IOTA can continue this work into the future. His foresight
in future proofing the design and implementation is greatly
appreciated.
I am also indebted to the many other workers who have taken
occultation observing and recording from its beginnings as a
private avocation to its present accepted status. Amateur
observers are now seen as a helpful adjunct to professional work
by the scientific community. Such acceptance is largely due to a
consistent emphasis on quality and reliability that the
occultation observer must of necessity put into the craft.
It is a privilege to be associated with such careful
workers, and I am glad my contribution has been of use.
Regards,
Tony Barry
Western Sydney Amateur Astronomy Group.
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 Derald Nye
from Arizona. Derald is an avid observer, who has travelled
worldwide for the most unusual occultations and eclipses. On
November 22, 1989 using binoculars, Derald timed an occultation
of a 7.1-mag. star by (15) Eunomia from the Amazon River, the
only asteroidal occultation known to have been observed from a
ship. On April 23, 1998, he and wife Denise observed the rare
simultaneous lunar occultations of Venus and Jupiter from
Ascension Island. On October 19, 2005, he timed an occultation of
Regulus by (166) Rhodope from Portugal along with several other
observers.
To date, he has seen 45 eclipses, and collected data on many of them for IOTA’s long term solar radius study. Derald has also helped with the early promotion of grazes and has maintained the Occultation Newsletter archives since the 1980’s.
Derald is a longtime member of the Association of Lunar
and Planetary Observers (ALPO) and the International
Amateur/Professional Photoelectric Photometry (IAPPP) group. He
is the recipient of the 2010 Leslie Peltier Award from the USA
based Astronomical League. Derald and his wife Denise also have
the honor of having asteroid 3685 Derdenye named in their honor.
It was discovered March 1, 1981 at Siding Spring Observatory, New
South Wales.
Richard Nugent spoke with Derald Nye a few days before
the meeting. Derald stays in an assisted living facility and is
wheelchair bound and thus cannot travel for occultations, however
his spirit is still very much alive and well. He was honored to
be chosen for the award and gave his sincere thanks.
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 Walt
‘Rob” Robinson. For several decades, Walt has provided
occultation predictions for observers. He has maintained
IOTA’s lunar occultation website since 1995, observed over
1,000 occultations, recovering 100’s of lost observations
confirming grazes of unknown stars, and has distributed Occult
software worldwide. In 2006, Walt co-authored the book with Hal
Povenmire, “Occultation Observer’s Handbook.”
Walt
sent the following after being notified of the award:
I am
highly yet humbly honored to receive this award. Over the past 30
some years I have always "looked forward" in new ways
of expanding IOTA's reach - from probably the first IOTA internet
site, establishing the old Yahoo messaging site to the current igroup
format, and being able to provide David Herald with a means of
distributing his Occult software. I would like to thank Robert
Sandy who helped me along the way and kept my interest in
occultation work. In the capacity of VP of Occultation Services,
I have been able to do the same with others world-wide. I will
continue to support the work of IOTA in whatever capacity I can
serve. Thank you."
Walt "Rob" Robinson
For
information on IOTA's awards, including previous awardees, see
the award webpage:
http://www.asteroidoccultations.com/observations/Awards/IOTAAwards.htm
Technical
sessions:
Alex Knox presented a talk “Automating
Telescopes to Observe Occultation Events”. Her
telescope system consisted of a Celestron NexStar5 with the StarSense
AutoAlign feature, the RunCam Night Eagle 2 Pro camera recording
on a Panasonic Toughbook computer through a USB port. The
telescope is moved via the computer using several software
programs to the target star. The basic sequence is:
1. IOTA’s video capture
software was used to record twice: first, as input for the plate
solve software and second, at the time of the event
2. ImageJ, an image processing
software, was used to convert the first recording by the video
capture software from its avi format to FITS format, which is
accessible to the plate solving software.
3. The plate solve was run on AstroTortilla,
a software driven by the Astrometry.net plate solver engine
These programs were chosen to ensure that all functions
needed to align the telescope to the target star can be done
entirely on a computer. Alex then showed a flowchart of how the
software specifically operates to get the proper FOV in the
telescope.
Tony George spoke on snatching the chords of the
229 Adelinda event from 2020 Jun 17. Tony showed his jagged light
curve he obtained which he first declared inconclusive. Using PyOTE,
Phil Stuart reported a 0.33 mag drop event and his position was
in line with Tony’s observation. Paul Maley’s
observation was analyzed by Tony and no event was found due to 1)
the small magnitude drop and 2) the high saturation of the target
star with the high integration used. Wayne Thomas sent his video
to Tony and using PyMovie, he found an event. Richard Nolthenius
also observed this occultation at 64x integration but was unsure
if he had an event. But he had a “blip” in the
light curve that indicated an event. When plotted with the rest
of the chords, his observation made a decent fit compared to the
other observations.
Tony George then spoke about use of a
digital noise reduction (DNR) with the Watec 910HX camera. He
basic message was to never us the 3DNR noise reduction option in
camera settings. Most chips inside our cameras pick up noise from
the other electronic components within the camera. DNR uses a
temporal noise reduction method and compares one frame to the
next for identifying noise pixels. The 3DNR has the effect of
applying a running average making occultation events appear
gradual instead of instantaneous. Eric Frappa also had similar
behavior (gradual events) in other videos and traced it to the
3DNR. He also is of the opinion that the 3DNR should not be used.
Tony mentioned that the Watec 910HX turns this feature on
automatically when turned on, so be sure to turn it off on start
up.
Bob Anderson talked about PyMovie: perspectives on the computed mask technique. The mask idea was to remove light from pixels that do not belong to the star. Thus Bob created PyMovie to help with star images that were smeared either from wind shake and/or rising hot air heating effects. A computed mask would cover the smeared star image vs. the classic circular mask common to both Limovie and Tangra. Bob showed an example video using PyMovie and how it removed noise pixels to help identify stars as compared to a star chart. He recommended using a background aperture in the star field to calibrate/verify that the target star tracking aperture is working well.
Bob then discussed the issues of false positives and the
normalization function when used with the target star and
comparison star with PyOTE. He discussed the normalization
function as applied to passing clouds and that a time shift would
need be used as the clouds would cover the comparison star at a
different time that the target star. Several questions came in
after Bob’s talk and he demonstrated the normalization
function and other useful features of PyOTE.
17:15
UT ---Lunch break----
18:15
UT ---Technical sessions continue
Suhas Gurjar from IOTA’s India Section presented a history of India’s occultation history. The first asteroid event observed was 1243 Pamela occultation results from Feb 2013. In Dec 2016 Paul Maley helped organize 20 video stations for the 22 Kalliope event. 8 chords were obtained and the result is shown below:
With no internet information for India occultations
events, on 3 May 2019, the India IOTA section was formed: http://iota-india.in/. India has very few observers, and Suhas is working on
expanding this. He has published articles in their local online
newspapers advertising such events. He also has a Facebook page advertising
India occultations.
For
event timings, they use a “Set Timer” cell phone app
which provides location latitude, longitude, altitude from GPS
and event time with a fraction of a second resolution. A main
hurdle in doing occultations is the equipment cost which runs
some $800. He is trying to get the cost down to $250 with the
help of Paul Maley, Steve Preston, Ted Blank, Hristo Pavlov, Dave
Herald, Tsutomu Hayamizu and IOTA.
Paul Maley then introduced Atila Poro from
Iran, President of IOTA/ME (Middle East) section.
He presented a history of the IOTA/ME section and some of the
observations and methods they use. He discussed their early video
timing methods with the help of Dave Gault as IOTA VTI’s and
other equipment is beyond the budget of many of their
observers. He talked about the work his members are doing now
including studying the sizes of 3 asteroids, TNO’s and other
objects. Some occultation techniques are being introduced
in schools.
Dr. David Dunham spoke on the best grazing occultations of the past year and best upcoming grazes 2020 and 2021. He started with the video of a spectacular graze of Aldebaran from March 5, 2017 in Canada. 5 observers made observations and a combined video of all the D and R’s was shown. He and Joan did 4 grazes in the past 2 years:
2018 July 10 – Aldebaran. They observed
from Mackinaw City, Michigan, with the Moon altitude of
just 7 deg. An unexplained north shift on the order of
0.02" (40-50 meters on the ground) was seen with the data
plotted. We had expected a similar-sized south shift, like was
observed at the 2016 July and 2017 March northern-limit grazes,
that we thought at the time was caused by proper motion errors of
Aldebaran. But since the shifts were in opposite directions,
that’s unlikely to be the explanation. The shifts may have
been caused by LRO/ LOLA data, or even modeling errors of the
Moon’s very complex gravity field for the LRO orbit
determination. It’s remarkable the small effects that we can
now study, with HIP/Gaia data for the stars and the extremely
detailed profiles that can be generated from the LRO/LOLA data.
.
2019
May 11, ZC 1298, they observed over 40 occultations that night. Plus
5 D and R’s with the m = +6.5 star ZC 1298.
2020
Jan 2, mag +4.6 33 Piscium, path crossed Phoenix, Arizona
area suburbs. They got 3 D’s and 4 R’s.
2020 Apr 28, Milky Way passage by the crescent Moon. From Fountain Hills, Arizona they observed some 26 occultations. Several stars were listed as double stars, but they didn’t see evidence of this in their observations. For a few of the brighter events, Joan and David ran their QHY camera at higher than video rates, resolving the “toe” of the Fresnel diffraction pattern.
David
then discussed future graze events for 2020 and 2021, Graze stars
mag +5.0 or brighter are published in JOA and stars
brighter than mag = +7.5 in the RASC Observer’s Handbook.
He showed several maps of the grazes over the USA from JOA
2020-4, page 21 and the 2020 World Map from http://iota.jhuapl.edu/GRAZEMAP.HTM
. He showed several maps of grazes predicted in the USA for 2021,
these will be in the 2021 RASC Observer’s Handbook.
President Steve Preston spoke on the best asteroid occultations for the upcoming year for North America. With Gaia star position data there is a higher probability of accuracy of asteroid event predictions. With the next Gaia update of asteroid positions, predictions should be even better by next year 2021.
103 Hera, m = +9.8 star, July 30, 2020
535
Montague, m = +9.0 star, July 31, 2020
106 Dione,
m = +8.8 star, Aug 3, 2020
552 Sigelinda, m = +9.8 star, Aug 20, 2020
SwRI – Eurybates, m = +14.5, Sep 16, 2020
109 Felicitas, m = +8.8, Oct 19, 2020
SwRI – ORUS, m = +16.1, Oct 21, 2020
593 Titania,
Oct 27, 2020, m = +9.5
171 Ophelia, m = +9.6, Nov 16, 2020
333 Hadenia
2 events on Nov 28, 2020, path intersections crossing in
southeast New Mexico
60558 Echeclus,
Jan 19, 2021 currently a large prediction error, Steve will
update
8
Flora, m = +7.2, Mar 18, 2021
Jupiter
Apr 2, 2021, m = +5.8 star 44 Cap, duration 72 minutes
6 Hebe, m = +8.2, Jul 27, 2021
191 Kolga, m = +7.1, Sep 7, 2021
762 Pulcova, m = +7.1, Sep 20, 2021
SwRI – Eurybates, m = +12.1, Oct 20, 2021
John Moore talked about the best observed North
American asteroid occultations for the past year. He started with
IOTA North American statistics 3-year summary. There is an
increasing trend of observations in the past 3 years 2017 –
2020.
Total
observations
Positive chords
Negative Chords
2017:
132
232
79
2018:
185
351
121
2019:
206
372
178
Busiest North American asteroid occultation observers in 2020 with # of chords:
David
and Joan Dunham – 67
Paul
Maley – 45
Roger
Venable – 33
Dave Oesper
– 26
Tony
George – 26
Steve
Messner – 25
John
Moore – 25
Wayne
Thomas – 23
Jerry
Bardecker – 18
Chris
Anderson – 17
2019’s most interesting observations:
3200 Phaethon 2019 Jul 29 – a total of 52 chords,
with 6 positives and 46 negatives. Chord coordination done by
David Dunham. Phaethon is the target for the JAXA Destiny mission
, launch date ~ 2022. Phaethon was captured again on Sep 29, 2019
16
Psyche, 10/24/2019 15 chords/15positives
527 Euryanthe,
1/20/2019, 13 chords, 6 positives
18 Melpomeme,
7/15/2019, 9 chords, 5 positives
144 Vibilia,
10/15/2019, 6 chords, Elizabeth Warner had 2 positives from the
same chord possibly indicating a graze of a mountain/valley
55
Pandora, 12/7/2019, 14 chords, 10 positives
11351
Leucu, 12/29/2019, 12 chords, 9 positives, this asteroid is a
target for the NASA Lucy mission, estimated launch date is
10/2021
624 Hektor,
8/28/2019, cross Atlantic observers, 11 chords, 6 positives
Dave Herald discussed the best non-North American asteroid occultations for the past year 2019. In 2019 worldwide asteroid occultation observations were over 500 and showing a growing trend the past few years. This increasing trend he showed with respect to the star catalogues used for predictions. Compared to the 1990’s the number of nonusable events has dropped significantly. This is because the 1990’s had lots of visual observations, whence the past 10 years we now use video and GPS based timing techniques.
He listed the number of worldwide asteroid observations vs. the average number of observations/event:
2017 939 observations, 334 events, 2.8 obs/event
2018 1490 observations, 504 events, 3.0 obs/event
2019 1666 observations, 586 events, 2.8 obs/event
Dave then showed world stats of asteroid observations by
region:
| 2019 | 2018 | 2017 | |
| Australasia | 132 | 142 | 68 |
| Europe | 171 | 148 | 95 |
| Japan | 56 | 34 | 22 |
| US | 287 | 183 | 130 |
| South America | 20 | 23 | 17 |
| Other | 22 | 15 |
............TOTAL 688
He mentioned double stars discovered during occultations are usually found in the 1 to 100 mas (milli-arc-second) range separation. Compare this to Gaia’s resolution of ~100 mas. He showed a list 8 double stars were discovered in 2019.
Dave
then showed 11 of the best profiles for 2019 and compared
occultation derived diameters vs. those of IR satellites::
984 Gretia 2019 Jan 17 Fitted diam: 36 km compared to IR satellites: 32 ± 3km
71 Niobe
2019 Feb 10 Fitted diam = 84km, IR satellites: 80 ± 10km
Neowise, 86 ± 6km AcuA, 83 ± 10km IRAS
334
Chicago, 2019 Feb 12 Fitted diam = 179 km IR satellite diam: 199
± 25km Neowise, 180 ± 13km AcuA, 159 ± 25km IRAS
145 Adeona 2019 Apr 22 Fitted diam = 142 km IR satellites: 127 ± 13km Neowise, 144 ± 21km AcuA, 151 ± 18km IRAS, has a double star 5.3 mas separation in PA = 133°
3200
Phaethon 2019 Jul 29 Fitted diam = 5.3 km IR satellite diam: 4.8
± 1.0km AcuA, 5.1 ± 0.6km IRAS, Dave mentioned that
gravitational deflection moved the actual location of the
asteroid approximately 1 diameter compared to the 3 predictions
made.
163 Erigone
2019 Aug 14 Fitted diam = 74 km IR satellites diam: 81 ±
11km Neowise, 74 ± 5km AcuA
624 Hektor
2019 Aug 28, Fitted diam = 181 km, Volume equiv diam = 125
km, IR satellite diam 147±17km Neowise, 212 ± 14km AcuA
247
Eukrate 2018 Oct 1, Fitted diam = 308 km, IR
satellite diam 305 ± 17km Neowise, 212 ± 14km AcuA
144
Vibilia 2019 Oct 15 Fitted diam = 144 km, IR satellite diam
155 ± 38km Neowise, 147 ± 11km AcuA, 142 ± 17km IRAS
16
Psyche 2019 Oct 24 Vol-equiv diam = 216 km, IR satellites diam:
288 ± 33km Neowise, 227 ± 20km AcuA, 253 ± 29km IRAS
87
Sylvia 2019 Oct 29 #1 , Fitted diam = 288km, IR satellites; 253 ±
28km Neowise, 262 ± 19km AcuA, 261± 29km IRAS
87
Sylvia 2019 Oct 29 #2, Romulus satellite: diam = 36x20 km,
Sep 0.513" in PA 75deg
87 Sylvia Remus satellite: Fitted diam = 13 x 9 km, Sep 0.265" in PA 91°
Steve Kerr spoke about recent occultations
happenings in Australia and New Zealand. Steve showed
specific regions of Australia and NZ where most occultation
observations are observed. Going back to 2008, he showed the
trend of observed events. There were 47 sucessful chords in 2008
and over the years increased to 180 sucessful chords in 2019. He
then showed profiles of some of the better observed asteroid
events, 349 Dembroska on 2019 Jun 18, 18 Melpomene on 2019 Oct 4,
925 Alponsina on 2019 Oct 23, 458 Hercynia on 2019 Dec 17.
-----meeting adjourned at 21:55 UT-----
Sunday July 26, 2020, meeting start 14:00 UT---
Kai Getrost discussed calibration issues with the
QHY 174. Calibration is important for timestamp accuracy, and
exposure accuracy (which could be off by 100ms). Calibration is
not a one time setting, when some camera settings are changed,
the calibration must be updated. Kai demonstrated how using the
built in LED with its pulses, he could calibrate to GPS time. He
also discussed why calibration was needed more often due to
occasional frozen time stamps and other issues. He showed several
reasons why “BadData” can mean a bad calibration and
stay that way. Kai recommended re-calibrating each time any combination
of settings (such as exposure) are changed. Kai then described several
calibration issues and how to resolve them.
He listed several references/resources on the QHY 174
camera: SharpCap forums: forums.sharpcap.co.uk
Dr. Christian Weber’s IOTA-ES Berlin workshop notes
on the QHY174: https//www.iota-es.de/qhy174gps_workshop.html
Kai next discussed tips and tricks when using the QHY174 camera – General Issues, Advice and Best Practices. Kai mentioned that the typical 12v power connector inserted in a car accessory adapter can cause problems: sometimes the tip comes up just short of connecting. His solution was to add a piece of solder to make it longer. He mentioned that more binning will not improve S/N ratios as it does with CCD cameras. Using binning has the risk of running out of dynamic range and this should be tested. He then showed pros/cons of FITS vs SER: FITS saves more GPS data, e.g. lat, long, end of exposure, etc. and is the preferred format for many organizations that files are sent to. SER doesn’t open as many files during capture and this may allow a faster capture rate.
Kai offered a few good practice hardware issues: Always connect to 12v power. This runs the TEC and fan. A cooler chip can vastly reduce hot pixels. One should always connect the camera at start of a session – this minimizes thermal shock for late camera power ups. A few other common sense things should be done also – secure all cables on scope with rubber bands/Velcro. And if it’s cold outside, use a zip lock bag to prevent condensation. He also talked about the pros/cons of a firmware upgrade. When in the field, ensure that an updated GPS almanac is downloaded, this could take 20 minutes. Do a test capture before the event to check for dropped frames. And after the event, check GPS time with another standard source such as WWV, Naval Observatory time clock.
Johnny Barton of the Central Texas Astronomical Society
offered IOTA a meeting location for 2022 in central Texas. They
have a research grade observatory (Meyer Observatory) with basic
facilities, lecture room and a 24" Cassegrain
telescope. In addition to monthly public star parties, they work
with McDonald Observatory and other professional observatories on
follow up observations on exoplanets, variable stars and other
research areas. Onsite facilities for 20-25 people are available.
Dr. Joan Dunham discussed using a 16" SkyWatcher telescope with the QHY174 camera. The 16" is a large heavy scope yet very portable which they move with a scope buggy. Joan talked about how they prepare to observe. First they collimate the telescope. They use a video finder aligned with the scope for later easy locating of target stars. A 2-star alignment is used for aligning the telescope. With the red sensitive chip of the RunCam camera, the FOV may not match the finder charts including the asteroid and target star - she advised to go ahead and get the data and reduce it later. Joan uses an observing table next to the telescope - its holds finder charts, batteries, computer, mouse, IOTA-VTI, flashlight, etc. Note that the table must be moved when the scope slews !
Joan’s next talk was methods of observing under constrained circumstances, such as when out in the field near a street light, public sidewalk, driveway or other non private places. She suggested having an assistant ready to answer questions to curious onlookers. Since June of this year, Joan and David tried 4 asteroid events from the sidewalk near their house: 803 Picka 2020 June 3, 2013 LU28 (miss), 466 Tsiphone 2020 July 2 (failed) and 53 Kalypso 2020 July 2 (miss). They have even done lunar occultations from their bedroom window.
Joan next talked about an equipment wish list: Enhanced pre-point charts on a laptop with night mode lighting instead of paper charts, display customizable to match screen display of FOV of scope, camera with IOTA-VTI GPS capabilities, onboard temporary capture to avoid dropped frames, and of course these should be inexpensive. Joan also mentioned that the USB 3.0 standard does not specify a maximum cord length but the maximum practical length for copper wiring to meet the electrical specs is 3m (9.8 ft).
David Dunham then talked about the Ode to
V1943 Sagittarii and how it foiled his station 3 observation
of the 303 Josephina eventon July 10, 2020. A few minutes before
the occultation, the problem was that the pattern of stars in the
FOV of his non-tracking 120mm “maxi” scope video (the
straight-through visual finder was useless in its position and
with some local light pollution) didn’t match the
finder chart near where the pre-point line was – in
the Terebellum asterism. The
problem was solved2 nights later when he imaged the FOV
with the Mighty Mini. Turns out the red sensitive RunCam camera
showed red stars not visible visually through his finder and this
was bit confusing especially when the occultation time draws
near. David showed a few slides with a method using Guide8/9 to
identify these red stars by using Guide’s option to show
variable stars.
At the NASA Small Bodies Assessment Group Conference in
January 2019, Marc Buie (SwRI) made a good case for officially
supporting occultation work. Professional astronomers took notice
with his talk and the publicity from SwRI’s 2017 and 2018 Arrokoth
(MU69) campaigns. Papers are due Aug 15, 2020 for the next
Astronomical Decadal Survey for proposed missions and Sep 15,
2020 for others. Marc Buie is tied up with the Lucy satellite
campaigns so David is working on a white paper for occultation
proposals and reached out to the participants for assistance.
David Dunham next talked about the 3200 Phaethon occultation from July 29, 2019 visible over California, Nevada and Colorado. It's the target of the Japanese Space Agency's (JAXA) DESTINY flyby in 2025, hence the need for occultation observations to provide an accurate position to refine it's orbit for the mission. Phaethon is of interest to planetary astronomers since it is the parent body of the active Geminidmeteor shower. Phaethon's small 5km size made predictions a challenge. The plan was to have 66 stations spread out over a 45 km range. Not all stations could be filled, and 11 didn't get any data. David and Joan Dunham set 11 stations of which 7 got data. Other observers were Scotty Deganhardt: 6 stations, Steve Preston (5 stations, 2 worked), John Moore/Steve Whitehurst (9 stations, all worked), R. Howard (3 stations - all worked), Jerry Bardecker (2 stations, 1 worked). A total of 52 stations got data and 11 stations failed for one reason or another. Here's the resulting occultation profile:
David then talked about the attempted 2019 Sep 29 occultation by Phaethon tried by 4 observers. The observations were too poor to improve on the size and shape of Phaethon but they did provide an astrometric point which matched the JPL Horizons Team solution 707 well. Two more events with Phaethon occurred on Oct 12, 2019 with an m =11.3 star, and Oct 15, 2019 over Japan where only two stations got data, 8 other stations had clouds.
David then showed his typical paver stone mount setup for remote stations and how it can reach stars to m = +13. A major advantage of the paver stone mounts is that the stones are sturdy, cheap, and can be pre-pointed the night before, then the scope carefully removed and the paver stone can be left at the site. For the Sept. 29th event, David and Joan took 3 paver stones (they fit under the driver’s and passenger’s seat of their RAV4) and brought them back home. But when paver stones are used for occultations when flying to the destination area, they buy them after arrival at a local Home Depot or similar (they cost less than $2 apiece), and they don’t try to bring them back.
David then discussed how asteroid orbits are improved
from asteroid occultations. This from a talk he gave at JPL while
he was in Pasadena for the NASA Small Bodies Assessment Group on
Jan 15, 2020. One such example occultation was the well observed87
Sylvia event from Oct 19, 2020.
He showed a few occultation observations that match generally closely with the DAMIT shape models. After a successfully observed occultation, a highly accurate astrometric position becomes available for both the star and asteroid. Along with the Gaia DR2 release (highest accurate star positions and proper motions to date) this has allowed further improvement on asteroid orbits for predicting a future event. David showed several observed asteroid occultations of how the accurate orbits and star positions have reduced the path errors significantly. Another remarkable example was the Pluto occultation of 2018 Aug 15 in which the predicted path shifted by just 8 km from the actual path from observations.
David showed a list of asteroids whose orbits have been
updated with Gaia and/or past occultations by the JPL Horizons
Team: 16 Psyche, 55 Pandora, 110 Lydia, 191 Kolga, 303 Josephina,
363 Padua, 456 Abnoba, 479 Caprera, 530 Turandot, 1400 Tirela,
and 3200 Phaethon. The 11351 Leucus orbit was updated by SwRI.
Vice President Dr. Roger Venable talked about strange light curves he gets from the Watec 910HX camera system. Roger first showed the difference of Limovie’s contour plots of unsaturated star peaks (pointed top) vs. saturated star peaks – (flat top). Using a certain analog to digital converter, he found that stellar images are double (2 closely spaced star images) with the Watec 910HX at 2x integration. Limovie’s contour plots verified this. He warned about the AVerMedia EZMaker analog-to-digital converter which causes the star images to appear double. These faulty converters also give up and down light curve plots which on first glance appear to be noise. Not only does this converter cause the up and down effect, it degrades the star image aspect ratio to change from circular to rectangular in shape. Roger learned that the more saturation, the less of the up and down effect in the light curve.
Tony George commented that with his Watec 910HX camera, he has never seen this up/down effect in the light curves, which includes hundreds of observations he has analyzed over the years. He suspected the capture device and/or cables could be the cause the sinusoidal effect in the light curves and not caused by the Watec 910HX camera. There was a disagreement on the origin of this effect as several other participants offered theories on what might be the source of this very strange anomaly.
Oliver Kloes (on behalf of Konrad Guhl, IOTA-ES
President) talked about IOTA-ES occultation activities.
IOTA-ES is a very active IOTA organization, observing over a
hundred occultations per year, publishing papers in JOA and
heavily involved in numerous activities. In 2019 they had 180
positive reports, in 2020 they already have 134 positive reports.
He highlighted the 2 Pallas 2020 June 22 event which had 34
positive chords. The 87 Sylvia event on 2019 Oct 29 was highly
successful which included observations of Sylvia’s 2 moons.
Oliver mentioned if you have any type of occultation report or
technique, please submit it to the JOA which is published
by IOTA-ES.
The European Symposium on Occultation projects (ESOP)
occurs this year on August 29/30, 2020. The meeting will be
online only due to the Covid-19 situation. ESOP is a highly
attended meeting, typically 70-80 people go. IOTA-ES recently
made a collective purchase of 31 QHY171M-GPS cameras. A workshop was
held on Feb 29, 2020 on how to use the camera with all of its
features and calibration settings.
IOTA-ES has also built a mobile 20" telescope
designed especially for occultation events. Other activities they
are involved in includesbeta testing DVTI, continuous SharpCap
testing as related to the QHY174 camera, timing of CMOS cameras
and other projects.
The
Meeting adjourned at 18:15 UT.
The minutes of all IOTA's annual meetings are at: http://www.poyntsource.com/Richard/IOTA_Annual_Meetings.htm
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.
