Hiraoka Occultation

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Hiraoka Occultation

• Pushing the limits on what a backyard observer
  can do with modest amateur equipment
• By Tony George
• Umatilla, Oregon

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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

• 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

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Photo of 12-inch LX200GPS Equipment
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Hiraoka Predicted Occultation
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Hiraoka Predicted Path
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Hiraoka Star Field as seen by PC164C video camera
Hiraoka Occultation Target Star
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Hiraoka Star Field Oriented to N-S
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Digitized Sky Survey photo of star field
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TheSky6 planetarium program view of star field
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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 .
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LiMovie to the rescue!

• I used LiMovie a new video analysis tool to
  analyze the video and find the extremely short
  occultation

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LiMovie Plot of target star intensity over time
period when occultation occurred
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Extraordinary claims require extraordinary proof.

• 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

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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_may20
  06/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.
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Based on the data provided and the independent
analysis by Dr. Michael RichmondDave 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
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Final Data Submitted

• Occultation Duration 0.20 seconds
• Calculated Diameter of the Asteroid 7 km
  assuming the widest part of the asteroid caused
  the occultation seen

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When the results were shared with the LiMovie
author, I Received Japanese Comments Regarding
the Hiraoka Observation

• 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.
• 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.
• 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.

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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 starsIn the future, we
should be observing occultations by
trans-Neptunian objects (TNOs) 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 (NEOs) that someday may be a
hazard to the Earth.
The Future of Occultations