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A Hartmann Differential Image Motion Monitor (H-DIMM) for Atmospheric Turbulence Characterisation

Published online by Cambridge University Press:  25 April 2016

John Bally ,
David Theil ,
Youssef Billawala ,
Dan Potter ,
R. F. Loewenstein ,
Fred Mrozek  and
James P. Lloyd
John Bally
Affiliation:
University of Colorado, Boulder, CO 80309, USAAstrophysical, Planetary, and Atmospheric Sciences Department, bally@casa.Colorado.EDU Center for Astrophysics and Space Astronomy (CASA) Center for Astrophysical Research in Antarctica (CARA)
David Theil
Affiliation:
University of Colorado, Boulder, CO 80309, USAAstrophysical, Planetary, and Atmospheric Sciences Department, bally@casa.Colorado.EDU Center for Astrophysics and Space Astronomy (CASA) Center for Astrophysical Research in Antarctica (CARA)
Youssef Billawala
Affiliation:
University of Colorado, Boulder, CO 80309, USAAstrophysical, Planetary, and Atmospheric Sciences Department, bally@casa.Colorado.EDU Center for Astrophysics and Space Astronomy (CASA) Center for Astrophysical Research in Antarctica (CARA)
Dan Potter
Affiliation:
University of Colorado, Boulder, CO 80309, USAAstrophysical, Planetary, and Atmospheric Sciences Department, bally@casa.Colorado.EDU Center for Astrophysics and Space Astronomy (CASA) Center for Astrophysical Research in Antarctica (CARA)
R. F. Loewenstein
Affiliation:
Yerkes Observatory, University of Chicago, Williams Bay, WI 53191, USA Center for Astrophysical Research in Antarctica (CARA)
Fred Mrozek
Affiliation:
Yerkes Observatory, University of Chicago, Williams Bay, WI 53191, USA Center for Astrophysical Research in Antarctica (CARA)
James P. Lloyd
Affiliation:
Yerkes Observatory, University of Chicago, Williams Bay, WI 53191, USA Center for Astrophysical Research in Antarctica (CARA) Joint Australian Centre for Astrophysical Research in Antarctica (JACARA)
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Abstract

We describe the use of a multi-aperture Hartmann mask coupled to a slightly out-of-focus focal plane array imager to monitor atmospheric turbulence (‘seeing’) produced by refractive index fluctuations. The imager (a CCD) is located inside or outside the focal surface of the imaging system so that each sub-aperture of the Hartmann mask produces an image well separated from all of the other images produced by the mask. Since the depth of focus of the sub-apertures is an order of magnitude larger than that of the parent optical system, the individual images are still diffraction-limited. We obtain short (10 to 100 msec) exposures and monitor the position fluctuations of the images. Analysis of the position and intensity fluctuations of the images can be used to determine the atmospheric parameter r0, the wind direction and velocity, and, under some circumstances, the distance of the turbulent layer from the observing site.

Keywords

instrumentation: turbulence monitoringsite testing: seeing
Type
The First JACARA International Antarctic Astronomy Meeting
Information
Publications of the Astronomical Society of Australia , Volume 13 , Issue 1 , January 1996 , pp. 22 - 27
Copyright
Copyright © Astronomical Society of Australia 1996

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References

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