Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

High-Resolution Imaging with a Tip-Tilt Cassegrain Secondary

L. M. Close and D. W. McCarthy, Jr.
Publications of the Astronomical Society of the Pacific
Vol. 106, No. 695 (1994 January), pp. 77-86
Stable URL: http://www.jstor.org/stable/40680244
Page Count: 10
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
High-Resolution Imaging with a Tip-Tilt Cassegrain Secondary
Preview not available

Abstract

A prototype adaptive secondary mirror has been developed on a 2.3-m telescope to stabilize rapid image motion caused by atmospheric turbulence. The instantaneous position of an image's centroid, or brightest speckle, is measured by a near-infrared camera system which enables the tip-tilt mirror to recenter the image. Correction is accomplished at closed-loop frequencies of ≤100 Hz on guide stars with (2.2 μm) magnitudes ≤8. Image motion is reduced to <0.̋1 rms, removing over 90% of low-frequency (f≤5 Hz) tilt power, leaving ≤1 rad² mean square wave front tilt phase error. In seeing conditions where D/r₀ ~ 4, long exposures in the H band (1.6 μm) exhibit a nearly diffraction-limited resolution of 0? 19 FWHM (Strehl ratio ~0.14)— a factor of 4 improvement over uncorrected images. Reduction of the present static optical errors will improve the Strehl ratio another factor of 2, leading to ~ 70% of the maximum possible Strehl ratio.

Page Thumbnails

  • Thumbnail: Page 
77
    77
  • Thumbnail: Page 
78
    78
  • Thumbnail: Page 
79
    79
  • Thumbnail: Page 
80
    80
  • Thumbnail: Page 
81
    81
  • Thumbnail: Page 
82
    82
  • Thumbnail: Page 
83
    83
  • Thumbnail: Page 
84
    84
  • Thumbnail: Page 
85
    85
  • Thumbnail: Page 
86
    86