A very successful observation of the asteroid occultation

PTS

Hi,
The sky went all clear just at the right moment to allow a very successful timing observation of this event:

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On 2009 Jun 17 UT, the 132 km diameter asteroid (146) Lucina will occult a 11.0
mag star in the constellation Virgo for observers along a path across New
Zealand, Australia, Indonesia, Philippines, Hong Kong, China.

In the case of an occultation, the combined light of the asteroid and the star
will drop by 2.1 mag to 12.9 mag (the magnitude of the asteroid) for at most
11.8 seconds.
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some 20 teachers from the Teachers' Class witness the asteroid Lucina moving towards the 11th mag star on the screen, then occult the star for some 8-9 seconds at the predicted moment, then actually seeing it came out of the glaze of the star some 7 minutes later...

I am analysing the AVI file and preparing the report.  I'll post it here later.

PTS

PTS

Hi,
I've finally been able to resolve the 5 GB AVI file.  The preliminary result is:

Start of occultation : 2009-06-17 12:25:31.45 UTC
End of occultation:    2009-06-17 12:25:41.83 UTC

PTS

CHYeung

Dear PTS,

Nice work.

How can you estimate the contact times and duration of occultation from this video?

YCH

PTS

CH,
I just extract the individual frames and inspect them one by one.  As I was using 15 fps, the error is about 1/15 seconds.
At the beginning, I used 6 fps to verify the targets.  When the asteroid was very vlose to the target star, I increased the frame rate until tha target star is just visible.  This is to improve the timing precision as well as to easier recognize the contact time from the frames.

BTW, the event for this morning was washed out.


PTS

CHYeung

Dear PTS,

Would you consider to use some sort of image analysis tool, such as IRIS? In my opinion, a cross sectional view of the pixel profile along the axis of encounter may help to pinpoint the moment of contacts.

YCH

PTS

CH,
I suppose image processing will not help as far as timing is concerned, as there is no way to extract intra-frame data.
However, there is a software that help analyse a sequence, and may extract a better inter-frame timing.  I'll try to learn to master that later.  Too busy these days preparing for the eclipse.

PTS

PTS

Hi,
My occultation data for Lucina on June 17, 2009 was analysed and the path of Lucina was updated.

PTS