Making and Observation of the Tohoku Univ. Antarctica DIMM

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Making and Observationof the Tohoku Univ.
Antarctica DIMM

• Hirofumi OKITA
• Astronomical Institute
• Tohoku Univ. (B4)

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Contents
Introduction DIMM Theory Tohoku
DIMM Observation Result Future work
Antarctica 40cm Telescope with the DIMM
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Introduction (1)
?The Seeing is defined as FWHM of stars at long
time exposure.
In Space, stars FWHM is Rayleigh limit.
Rayleigh limit Actually seeing
Subaru Telescope 0.06" 0.3"
But
The case of the grand base observation, wavefront
from the star is not parallel.
So the star size is not Rayleigh limit, but
expanded image by the air turbulence.
?It is important to choice Good Seeing Site.
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Introduction (2)
Antarctica
The last window to the Universe
Cord
IR Background is very low, and NIR transimittance
is very high
?
Dry
Many fine days Good seeing
Calm weather Downdraft
?
Dome C(Alt.3250m) 0.54
Dome Fuji(Alt.3810m) ?0.5 ??
However, the site testing at Dome Fuji has not
been done yet.
I made the DIMM, and want to get actually seeing
size.
http//en.wikipedia.org/wiki/Showa_Base
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DIMM
Classical DIMM(Differential Image Motiron
Monitor) has 2 apature.
Star light
?
The phase shifts by air turbulence
?
DIMM
?
Image of two stars
?
Measurement of relative position
?
Convert them into seeing value
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Theory (1)
Star light at SpaceParallel
?
Air turbulencewavefront
phase error
Angle of arrival fluctuation
Covariance of a
Covariance of f
Phas structure function
Kolmogorov turbulence ?
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Theory (2)
Change the angle of arrival fluctuation
Change in position of stars
Relationship between
and FWHM
Zenith angle correction
It calculates
DAperture Diameter dseparation two aperture
?From We obtain Seeing size.

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DIMM Hardware
Unlike a classical DIMM, Tohoku DIMM is Four
aperture DIMM to get more information of a
turbulence layer.
Antarctica 40cm Telescope Antarctica 40cm Telescope
Aperture 400mm
Focal length 5190mm
DIMM
Separation of diagonal apertures d 250mm
Aperture diameter D 74mmmm
Apex angle of Wedge prism 30arcsec
Wat-100N (Watec Co., Ltd.) Min. 0.001 lx, and
Exp. time/gain/gamma Manually changeable
Pixel size Pixel size
Horizontal 0.3903arcsec/pix
Vertical 0.4553arcsec/pix
Expose time 1/1000s
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DIMM Software
Software was Developed by Dr. Motohara ( Research
Associate, University of Tokyo)
Dr.Motohara and UT-DIMM
His Software
From His software we can get analyzed data
(seeing size arcsec) but zenith angle is not
corrected, so I made zenith angle correction
software.
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Observation
Jan 13 2008 Measurement of Pixel size Jan 16
2008 Observation at Sendai Feb 10 2008
Observation at Rikubetsu ( Hokkaido, the North
island of Japan) Feb 14 2008 Observation at
Rikubetsu
Movies
Star
Saturn
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Result (1)
Jan 16 2008 Observation at Sendai
Sendai
Average 2.09
Median 2.03
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Result (2)
Feb 10 2008 Observation at Rikubetsu
Rikubetsu
Average 1.49
Median 1.48
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Result (3)
Feb 16 2008 Observation at Rikubetsu
Rikubetsu
Average 2.81
Median 2.79
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Future Work
More Observation
change in a day change in a season
Comparison with Hiroshima Univ. DIMM
Check the Value is reasonable
Cold Test
Hiroshima Univ. DIMM
Camera AD converter PC ,etc.
We observe more and more at Sendai, and get
knowhow and technique.
?
2010 Observation at Dome Fuji