Transcript Hiraoka Occultation Report

Hiraoka Occultation
Pushing the limits on what a
backyard observer can do with
modest amateur equipment
By Tony George
Umatilla, Oregon
Background
Observing occultations for 20 years
 In 20 years I have contributed 8 positive
observations
 While I attempt to observe every possible
event, good opportunities in the Pacific
Northwest are few and far between.
 To keep in practice, I often try to observe
occultations of asteroids as small as 4 km
in size
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Methodology
Once every few months I run an updated
prediction of occultations visible from my
home site using WinOccult developed by
David Herald of Australia
 I select all numbered asteroids larger than
4 km in size
 I select all occultation paths that are within
50 km of my home site
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Equipment
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Meade LX200GPS 12-inch telescope
Meade f3.3 focal reducer
WAT 902H2 Ultimate or Supercircuits PC164C
security video camera
STV Astro (or KIWI OSD) GPS video time
inserter
Garmin 16 GPS receiver (or Garmin 18 with
KIWI OSD)
Canon ZR50 Mini DV tape recorder
Battery pack
Photo of 12-inch
LX200GPS Equipment
Canon ZR50 Mini DVR
Garmin GPS16 Receiver
Meade f3.3 focal reducer
WAT 902H2 Ultimate
Video Camera w/manual
Gain control (can also use
Supercircuits PC164C or
CCD camera in drift scan
Mode)
STV Astro video time
inserter (most now use
KIWI OSD)
12V DC Battery pack
Hiraoka Predicted Occultation
Hiraoka Predicted Path
Hiraoka Star Field as seen by
PC164C video camera
Hiraoka Occultation
Target Star
Hiraoka Star
Field Oriented
to N-S
Digitized
Sky
Survey
photo of
star field
TheSky6 planetarium program view of star field
Hiraoka Observation
Began recording 3 minutes before
predicted time of event
 Recorded until 3 minutes after event
 Due to predicted max duration of 0.2
seconds, the occultation was not visible to
the eye when reviewing the video tape
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Here is how it looked ….
LiMovie to the rescue!
I used LiMovie a new video analysis
tool to analyze the video and find the
extremely short occultation
LiMovie Plot of target
star
intensity
overDatatime period when
Target Star Only
-- Raw
Data and Moving Average
occultation occurred
3500
3000
2500
2000
1500
1000
500
0
1
144 287 430 573 716 859 1002 1145 1288 1431 1574 1717 1860 2003 2146 2289 2432 2575 2718 2861 3004 3147 3290 3433 3576
Target Star LiMovie Aperture Data
10 per. Mov. Avg. (Target Star LiMovie Aperture Data)
Extraordinary claims require
extraordinary proof….
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The claim to see a 0.2 second occultation is very
extraordinary
While LiMovie plot shows a likely occultation, the
noise in the data might also be the cause of the
extended drop in light intensity
Comparisons to the other two field stars did not
show any similar drop in light intensity
An outside independent analyst volunteered to
review the data to determine if an occultation
occurred
An independent analysis of my report was
conducted by Dr. Michael Richmond of
the Dept. of Physics Rochester Institute of
Technology
Here is a link to his webpage documenting his analysis:
http://spiff.rit.edu/richmond/occult/hiraoka_may2006/hiraoka_may2006.html
His conclusion:
“I agree with Tony's conclusion: the
asteroid occulted the star for 7 frames,
which is equivalent to 14 fields.”
Based on the data provided and
the independent analysis by
Dr. Michael Richmond
Dave Herald of IOTA accepted the
data for submission to the Minor
Planet Center (MPC) – this is the
shortest single-chord event ever
submitted to the MPC
Final Data Submitted
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Occultation Duration
0.20 seconds
Calculated Diameter of
the Asteroid = 7 km –
assuming the widest
part of the asteroid
caused the occultation
seen
When the results were shared with the LiMovie
author, I Received Japanese Comments
Regarding the Hiraoka Observation:
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Yoshihiro Yamada who is the discoverer of the Hiraoka asteroid wrote:
I am very glad to know this. Because it is the first success observation
of the asteroids which is discovered by me.
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Tsutomu Hayamizu , who is the one of the coordinators of asteroid's
occultation in Japan, wrote: I ask you to inform him "Congratulation
on your observation success!" Only 14 fields.. I think we are entering a
new era of occultation observation. And we learned many things from
his preparation and his observation.
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Hiromi Hamanowa, the most successful observer of asteroidal
occultations in Japan wrote: Great work! It seems distinctly the light
curve different from the one which is influence by air scintillation. It
shows us how to use Limovie at its best performance. Highly accurate
orbital element will be obtained from only one observation. I think this
to be extremely meaningful observation. I entertain a profound respect
for Tony's spirit and his effort.
The Future of Occultations
We are just beginning to stretch the limits of what can be
done with modest amateur equipment. As video cameras
are improved we can observe events involving fainter
stars
In the future, we should be observing occultations by
trans-Neptunian objects (TNO’s) – those diminutive
objects out in the Kuiper belt beyond the orbit of Neptune.
We may also contribute vital information on the size and
shape of Near Earth Objects (NEO’s) that someday may
be a hazard to the Earth.