Abstract

By adjusting the optical path lengths of its individual beams, it is possible to make the multiple mirror telescope (MMT) into a phased array with a 6.86-m base line. A coherent phased focus can be achieved with tilted focal planes if the tilt angle is chosen so that the internal phase differences exactly compensate the external phase differences. This amounts to a slight change in configuration so that the beams are brought together at f/8.39 rather than the originally designed f/9. We summarize experiments which have used the MMT subapertures as a phased array and as a coherent phased telescope and present a simple analysis of the titled focal plane geometry for coherent observation. The phased operation of the MMT is important not only for obtaining high angular resolution but also for obtaining the higher detection sensitivity which results from the better discrimination against the sky emission background for IR diffraction-limited images. Full-aperture (six-beam) diffraction-limited results for the unresolved source Gama Orionis, the well-known close binary Capella, and the resolved red supergiant Betelgeuse (including a diffraction-limited differential speckle image of the latter) are presented as preliminary demonstration of the potential capabilities of this configuration.

© 1985 Optical Society of America

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References

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  1. A. Labeyrie, “Coherent Arrays,” in Optical Telescopes of the Future (ESO/CERN, Geneva, 1977).
  2. J. Davis, “An 11 Metre Michelson Stellar Interferometer,” NZ J. Sci. 22, 451 (1983).
  3. B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).
  4. A. Schulz et al., “Report on Submillimeter Spectroscopy (870 microns) using the MMT,” MMTO Observers’ Report, May 1984(Multiple Mirror Telescope Observatory, Tucson, 1984).
  5. D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).
  6. J. M. Beckers, F. Roddier, C. Roddier, “May 8/9 Rotation Shearing Interferometer Test,” MMTO Observers’ Report, May 1982 (Multiple Mirror Telescope Observatory, Tucson, 1982).
  7. F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
    [CrossRef]
  8. E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
    [CrossRef]
  9. J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).
  10. D. W. McCarthy, “MMT Polarization Properties,” MMTO Technical Memorandum 80-6, (Multiple Mirror Telescope Observatory, Tucson, 1980).
  11. J. M. Beckers, “Differential Speckle Interferometry,” Opt. Acta 29, 361 (1982).
    [CrossRef]
  12. H. A. McAlister, “The Apparent Orbit of Capella,” Astron. J. 86, 795 (1981).
    [CrossRef]
  13. A. Labeyrie, “Attainment of Diffraction-Limited Resolution in Large Telescopes by Fourier Analysing Speckle Patterns,” Astron. Astrophys. 6, 85 (1970).
  14. A. Labeyrie, “Stellar Interferometry Methods,” Ann. Rev. Astron. Astrophys. 16, 77 (1978).
    [CrossRef]
  15. C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
    [CrossRef]
  16. J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).
  17. A. B. Meinel, M. P. Meinel, N. J. Woolf, “Multiple Aperture Telescope Diffraction Images,” in Applied Optics and Optical Engineering, Vol. 9, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1982), p. 149.
    [CrossRef]
  18. J. R. P. Angel, “Very Large Ground-Based Telescopes for Optical and IR Astronomy” Nature London 295, 651 (1982).
    [CrossRef]
  19. J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

1984 (1)

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

1983 (3)

J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

J. Davis, “An 11 Metre Michelson Stellar Interferometer,” NZ J. Sci. 22, 451 (1983).

J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).

1982 (5)

J. M. Beckers, “Differential Speckle Interferometry,” Opt. Acta 29, 361 (1982).
[CrossRef]

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

J. R. P. Angel, “Very Large Ground-Based Telescopes for Optical and IR Astronomy” Nature London 295, 651 (1982).
[CrossRef]

1981 (1)

H. A. McAlister, “The Apparent Orbit of Capella,” Astron. J. 86, 795 (1981).
[CrossRef]

1978 (2)

F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
[CrossRef]

A. Labeyrie, “Stellar Interferometry Methods,” Ann. Rev. Astron. Astrophys. 16, 77 (1978).
[CrossRef]

1976 (1)

C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
[CrossRef]

1970 (1)

A. Labeyrie, “Attainment of Diffraction-Limited Resolution in Large Telescopes by Fourier Analysing Speckle Patterns,” Astron. Astrophys. 6, 85 (1970).

Angel, J. R. P.

J. R. P. Angel, “Very Large Ground-Based Telescopes for Optical and IR Astronomy” Nature London 295, 651 (1982).
[CrossRef]

Beckers, J. M.

J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).

J. M. Beckers, “Differential Speckle Interferometry,” Opt. Acta 29, 361 (1982).
[CrossRef]

J. M. Beckers, F. Roddier, C. Roddier, “May 8/9 Rotation Shearing Interferometer Test,” MMTO Observers’ Report, May 1982 (Multiple Mirror Telescope Observatory, Tucson, 1982).

Christou, J. C.

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

Cocke, W. J.

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

Davis, J.

J. Davis, “An 11 Metre Michelson Stellar Interferometer,” NZ J. Sci. 22, 451 (1983).

Demarq, J.

F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
[CrossRef]

Erickson, N. R.

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Freeman, J.

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

Goldsmith, P. F.

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Harvey, J. W.

C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
[CrossRef]

Hege, E. K.

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).

J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

Hubbard, E. N.

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

Huguenin, G. R.

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Labeyrie, A.

A. Labeyrie, “Stellar Interferometry Methods,” Ann. Rev. Astron. Astrophys. 16, 77 (1978).
[CrossRef]

A. Labeyrie, “Attainment of Diffraction-Limited Resolution in Large Telescopes by Fourier Analysing Speckle Patterns,” Astron. Astrophys. 6, 85 (1970).

A. Labeyrie, “Coherent Arrays,” in Optical Telescopes of the Future (ESO/CERN, Geneva, 1977).

Lada, C. J.

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Low, F. J.

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

Lynds, C. R.

C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
[CrossRef]

McAlister, H. A.

H. A. McAlister, “The Apparent Orbit of Capella,” Astron. J. 86, 795 (1981).
[CrossRef]

McCarthy, D. W.

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

D. W. McCarthy, “MMT Polarization Properties,” MMTO Technical Memorandum 80-6, (Multiple Mirror Telescope Observatory, Tucson, 1980).

Meinel, A. B.

A. B. Meinel, M. P. Meinel, N. J. Woolf, “Multiple Aperture Telescope Diffraction Images,” in Applied Optics and Optical Engineering, Vol. 9, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1982), p. 149.
[CrossRef]

Meinel, M. P.

A. B. Meinel, M. P. Meinel, N. J. Woolf, “Multiple Aperture Telescope Diffraction Images,” in Applied Optics and Optical Engineering, Vol. 9, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1982), p. 149.
[CrossRef]

Murphy, H. P.

J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

Roddier, C.

F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
[CrossRef]

J. M. Beckers, F. Roddier, C. Roddier, “May 8/9 Rotation Shearing Interferometer Test,” MMTO Observers’ Report, May 1982 (Multiple Mirror Telescope Observatory, Tucson, 1982).

Roddier, F.

F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
[CrossRef]

J. M. Beckers, F. Roddier, C. Roddier, “May 8/9 Rotation Shearing Interferometer Test,” MMTO Observers’ Report, May 1982 (Multiple Mirror Telescope Observatory, Tucson, 1982).

Schulz, A.

A. Schulz et al., “Report on Submillimeter Spectroscopy (870 microns) using the MMT,” MMTO Observers’ Report, May 1984(Multiple Mirror Telescope Observatory, Tucson, 1984).

Strittmatter, P.

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

Strittmatter, P. A.

J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

Ulich, B. L.

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Woolf, N. J.

A. B. Meinel, M. P. Meinel, N. J. Woolf, “Multiple Aperture Telescope Diffraction Images,” in Applied Optics and Optical Engineering, Vol. 9, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1982), p. 149.
[CrossRef]

Worden, S. P.

C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
[CrossRef]

Ann. Rev. Astron. Astrophys. (1)

A. Labeyrie, “Stellar Interferometry Methods,” Ann. Rev. Astron. Astrophys. 16, 77 (1978).
[CrossRef]

Astron. Astrophys. (1)

A. Labeyrie, “Attainment of Diffraction-Limited Resolution in Large Telescopes by Fourier Analysing Speckle Patterns,” Astron. Astrophys. 6, 85 (1970).

Astron. J. (1)

H. A. McAlister, “The Apparent Orbit of Capella,” Astron. J. 86, 795 (1981).
[CrossRef]

Astrophys. J. (1)

C. R. Lynds, S. P. Worden, J. W. Harvey, “Digital Image Reconstruction Applied to Alpha Orionis,” Astrophys. J. 207, 174 (1976).
[CrossRef]

Bull. Am. Astron. Soc. (1)

J. C. Christou, E. K. Hege, J. Freeman, P. Strittmatter, “Speckle Image Reconstruction: Weighted Shift-and-Add Analysis,” Bull. Am. Astron. Soc. 16, 885 (1984).

J. Opt. Paris (1)

F. Roddier, C. Roddier, J. Demarq, “A Rotation Shearing Interferometer with Phase-Compensated Roof Prisms,” J. Opt. Paris 9, 145 (1978).
[CrossRef]

Nature London (1)

J. R. P. Angel, “Very Large Ground-Based Telescopes for Optical and IR Astronomy” Nature London 295, 651 (1982).
[CrossRef]

NZ J. Sci. (1)

J. Davis, “An 11 Metre Michelson Stellar Interferometer,” NZ J. Sci. 22, 451 (1983).

Opt. Acta (2)

E. K. Hege, E. N. Hubbard, P. A. Strittmatter, W. J. Cocke, “The Steward Observatory Speckle Interferometry System,” Opt. Acta 29, 701 (1982).
[CrossRef]

J. M. Beckers, “Differential Speckle Interferometry,” Opt. Acta 29, 361 (1982).
[CrossRef]

Proc. Soc. Photo-Opt. Instrum. Eng. (3)

J. M. Beckers, E. K. Hege, P. A. Strittmatter, “Optical Interferometry with the MMT,” Proc. Soc. Photo-Opt. Instrum. Eng. 444, 85 (1983).

D. W. McCarthy, P. A. Strittmatter, E. K. Hege, F. J. Low, “MMT as an Optical-Infrared Interferometer and Phased Array,” Proc. Soc. Photo-Opt. Instrum. Eng. 332, 57 (1982).

J. M. Beckers, E. K. Hege, H. P. Murphy, “The Differential Speckle Interferometer,” Proc. Soc. Photo-Opt. Instrum. Eng. 445, 462 (1983).

Proc., Soc. Photo-Opt. Instrum. Eng. (1)

B. L. Ulich, C. J. Lada, N. R. Erickson, P. F. Goldsmith, G. R. Huguenin, “The First Submillimeter Phased Array,” Proc., Soc. Photo-Opt. Instrum. Eng. 332, 72 (1982).

Other (5)

A. Schulz et al., “Report on Submillimeter Spectroscopy (870 microns) using the MMT,” MMTO Observers’ Report, May 1984(Multiple Mirror Telescope Observatory, Tucson, 1984).

J. M. Beckers, F. Roddier, C. Roddier, “May 8/9 Rotation Shearing Interferometer Test,” MMTO Observers’ Report, May 1982 (Multiple Mirror Telescope Observatory, Tucson, 1982).

D. W. McCarthy, “MMT Polarization Properties,” MMTO Technical Memorandum 80-6, (Multiple Mirror Telescope Observatory, Tucson, 1980).

A. Labeyrie, “Coherent Arrays,” in Optical Telescopes of the Future (ESO/CERN, Geneva, 1977).

A. B. Meinel, M. P. Meinel, N. J. Woolf, “Multiple Aperture Telescope Diffraction Images,” in Applied Optics and Optical Engineering, Vol. 9, R. R. Shannon, J. C. Wyant, Eds. (Academic, New York, 1982), p. 149.
[CrossRef]

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Figures (21)

Fig. 1
Fig. 1

Lower left: cross section of the MMT entrance aperture (vertical in figure is vertical on the sky). Central figure: coverage in the Fourier transform plane, or (u,υ) plane, at a 500-nm wavelength if the six telescopes are phased.

Fig. 2
Fig. 2

As Fig. 1 but when only using two (or three) beams.

Fig. 3
Fig. 3

Ways of adjusting path lengths of individual beams: A, by longitudinal translation of the secondary hyperbolic mirrors. This may defocus the image by an intolerable amount; B, by sideways translation of beam combiner in two orthogonal directions. This allows phasing only for up to three telescopes; C, by inserting in each beam two complimentary wedges and translating one with respect to the other; D, by separating the six reflecting surfaces of the beam combiner and translating/tilting them. Drawing is not to scale.

Fig. 4
Fig. 4

Pupil shearing interferometer pupil fringes. A rotational shear has superimposed adjacent MMT subpupils. The actual fringe contrast (and coverge in the overlap region) is much greater than suggested in this vidicon image, which, because of video lag effects, is an integration for longer than the fringe correlation time set by the atmosphere.

Fig. 5
Fig. 5

Specklegram of a point source obtained with an opposite pair of phased beams. The nearly vertical interference fringes are 27 msec of arc apart (650-nm wavelength).

Fig. 6
Fig. 6

Image power spectrum of 300 specklegrams of a point source using two phased telescopes as shown in Fig. 2. The interferometer frequencies are shown clearly as the autocorrelation of the two-mirror pupil. The high-frequency background is the detector-colored noise bias.

Fig. 7
Fig. 7

Multiple mirror telescope specklegram produced when all six beams are cophased. All interferometer frequencies are seen simultaneously only in regions where light (single-mirror speckles) from all six telescopes is superimposed.

Fig. 8
Fig. 8

Image power spectrum of 500 specklegrams of a point source, β Tau, observed in a 10-nm bandpass centered at 750 nm using all six beams, as shown in Fig. 1. This is a measure of the actual speckle MTF for the MMT, including atmospheric effects, noise bias, and specklegram apodizing induced artifacts. (The unfortunate horizontal and vertical artifacts were induced by a software error which caused apodizing in the image plane by an inappropriate rectangular window.)

Fig. 9
Fig. 9

Each figure represents a fringe sample; (a) fringes at the top of the seeing distribution and the sample at the top of the raster; (b) fringes at the bottom, sample at center; (c) yet another fringe sample. Note that there are nine possibilities in the scheme.

Fig. 10
Fig. 10

One-dimensional square Fourier modulus for an unresolved star using an opposite MMT mirror pair. The line segment and shaded area define the integrated signal calculated by our fringe contrast detection algorithm.

Fig. 11
Fig. 11

Change of path length for all six telescopes as a function of elevation while repeatedly moving up and down.

Fig. 12
Fig. 12

Change of path length between telescopes B and E as a function of time while tracking a star in the western hemisphere: ⊙, raw data; ×, the same data after correction for the elevation change shown in Fig. 11. The remaining variation of the crosses is mostly due to changes in the mount (OSS) thermal structure.

Fig. 13
Fig. 13

Path length difference between telescopes B and E as a function of temperature difference. The dashed line corresponds to 65 μm/°C.

Fig. 14
Fig. 14

Schematic of optical paths in MMT for two telescopes I and II: D, geometrical separation of centers of telescopes; d, geometrical diameter of single telescope; 2 α, angles which principal rays make in the final image; δ, angle of the off-axis star-to-telescope axis; Δ, distance of off-axis star image to center of image plane.

Fig. 15
Fig. 15

Tilted focal planes of two single telescopes shown with reference to the detector focal plane, which is the mean focal plane for all telescopes. P is at the focus of the principal ray for an on-axis image. A and B are focal points at the center and edge, respectively, in a seeing-limited off-axis image.

Fig. 16
Fig. 16

Capella. Image power spectrum obtained from speckle-grams using the full 6.86-m MMT aperture in a 10-nm bandpass centered at 750 nm (compare with Fig. 8).

Fig. 17
Fig. 17

Two-dimensional visibility function for Capella. The theoretical aperture cutoff is represented by its circumscribing hexagonal border. This result is obtained by dividing the power spectrum shown in Fig. 16 by that shown in Fig. 8.

Fig. 18
Fig. 18

Capella photometry. The visibility data (+) are the average of 32 cuts perpendicular to the visibility fringes (i.e., parallel to line shown superimposed A-A′ on Fig. 17). The model is a cosine curve fit to the data in the region within the diffraction cutoff (vertical line). The standard errors in the fit are indicated by the shading. This analysis yields the results in Table II.

Fig. 19
Fig. 19

Multiple mirror telescope point spread function. This is the observed image for the unresolvable star γ Ori using our speckle image reconstruction variant of the shift-and-add method. The central response has FWHM = 20 msec of arc consistent with the 6.86-m aperture and the 656.3-nm observing bandpass. The hexagonal sidelobe response expected for the six-beam pupil is shown superimposed, as expected, on the Airy pattern for the circular single-beam response whose first minimum and first secondary ring are clearly shown. The horizontal and vertical artifacts are produced by the sensitivity of our image reconstruction algorithm to the ~0.65-sec of arc apodizing window imposed by the video digitizer on the ~1.5-sec of arc seeing. 1000 frames of data were processed. Scale: 5 msec of arc/pixel.

Fig. 20
Fig. 20

Differential speckle image of the unresolved source γ Ori showing the nearly diffraction-limited 15-msec of arc (FWHM) point spread function of the full 6.86-m aperture. Scale: 5 msec/pixel.

Fig. 21
Fig. 21

Differential speckle image of α Ori (Betelgeuse) showing a significant resolved structure at diameters to 100 msec of arc. The photon and atmospheric statistics in this preliminary sample of ~1000 frames of data limit this result to an effective signal maximum to a rms background noise ratio of ~10:1. Scale: 5 msec of arc/pixel (compare with Fig. 20).

Tables (2)

Tables Icon

Table I Fringe Contrast Sensing Experiments

Tables Icon

Table II Speckle Interferometry of Capella

Equations (2)

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CS = FT ( L ) · FT * ( C ) ; PS = | FT ( C ) | 2 ,
DSI = FT 1 ( CS / PS ) .

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