Abstract

Interferometric tests of an f/1.2, 2.5-m-diameter liquid mirror show rms surface deviations of ∼λ/20 and Strehl ratios of the order of 0.6, which show that it is diffraction limited. The mirror is certainly better than what is implied by the data because of aberrations introduced by the auxiliary testing optics. We made detailed studies of the scattered light of the mirror. We studied the behavior of the mirror under external perturbations. We reached an important milestone because we now have a good understanding of liquid mirrors.

© 1997 Optical Society of America

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References

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  1. E. F. Borra, “The liquid-mirror telescope as a viable astronomical tool,” J. R. Astron. Soc. Can. 76, 245–256 (1982).
  2. E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
    [CrossRef]
  3. E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
    [CrossRef]
  4. R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
    [CrossRef]
  5. P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
    [CrossRef]
  6. R. J. Sica, S. Sargoytchev, E. F. Borra, L. Girard, S. Argall, C. T. Sarrow, S. Flatt, “Lidar measurements taken with a large aperture liquid mirror: 1. The Rayleigh-scatter system,” Appl. Opt. 34, 6925–6936 (1995).
    [CrossRef] [PubMed]
  7. R. Wuerker, “Bistatic LMT lidar alignment,” Opt. Eng. 36, 1421–1424 (1997).
    [CrossRef]
  8. N. M. Ninane, C. A. Jamar, “Parabolic liquid mirrors in optical shop testing,” Appl. Opt. 35, 6131–6139 (1996).
    [CrossRef] [PubMed]
  9. L. Girard, “Etude d’un miroir liquide de 2.5 mètres de diamètre,” Ph.D. thesis (Université Laval, Québec, Canada, 1997).
  10. E. F. Borra, “Liquid mirrors,” Can. J. Phys. 73, 109–125 (1995).
    [CrossRef]
  11. S. Mallick, “Common-path interferometers,” in Optical Shop Testing, D. Malacara, ed. (Wiley, New York, 1978), Chap. 3.
  12. R. V. Shack, G. H. Hopkins, “The Shack interferometer,” Opt. Eng. 18, 226–228 (1979).
    [CrossRef]
  13. C. Roddier, F. Roddier, “Interferogram analysis using Fourier transform techniques,” Appl. Opt. 26, 1668–1673 (1987).
    [CrossRef] [PubMed]
  14. R. Content, “Tests optiques sur un miroir liquide de 1.5 m et développement de la technologie des miroirs liquides,” Ph.D. thesis (Université Laval, Québec, Canada, 1992).
  15. E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
    [CrossRef]
  16. W. B. Wetherell, in Applied Optics and Optical Engineering, Vol. 8, R. R. Shannon, J. Wyant, eds. (Academic, New York, 1980), Chap. 5.

1997 (1)

R. Wuerker, “Bistatic LMT lidar alignment,” Opt. Eng. 36, 1421–1424 (1997).
[CrossRef]

1996 (1)

1995 (2)

1994 (1)

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

1993 (1)

E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
[CrossRef]

1992 (1)

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

1989 (1)

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

1987 (1)

1985 (1)

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

1982 (1)

E. F. Borra, “The liquid-mirror telescope as a viable astronomical tool,” J. R. Astron. Soc. Can. 76, 245–256 (1982).

1979 (1)

R. V. Shack, G. H. Hopkins, “The Shack interferometer,” Opt. Eng. 18, 226–228 (1979).
[CrossRef]

Argall, S.

Arsenault, R.

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

Beauchemin, M.

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

Boily, E.

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Borra, E. F.

R. J. Sica, S. Sargoytchev, E. F. Borra, L. Girard, S. Argall, C. T. Sarrow, S. Flatt, “Lidar measurements taken with a large aperture liquid mirror: 1. The Rayleigh-scatter system,” Appl. Opt. 34, 6925–6936 (1995).
[CrossRef] [PubMed]

E. F. Borra, “Liquid mirrors,” Can. J. Phys. 73, 109–125 (1995).
[CrossRef]

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
[CrossRef]

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

E. F. Borra, “The liquid-mirror telescope as a viable astronomical tool,” J. R. Astron. Soc. Can. 76, 245–256 (1982).

Cabanac, R.

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

Content, R.

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
[CrossRef]

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

R. Content, “Tests optiques sur un miroir liquide de 1.5 m et développement de la technologie des miroirs liquides,” Ph.D. thesis (Université Laval, Québec, Canada, 1992).

Drinkwater, M. J.

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Flatt, S.

Gauthier, A.

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Gibson, B. K.

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

Girard, L.

R. J. Sica, S. Sargoytchev, E. F. Borra, L. Girard, S. Argall, C. T. Sarrow, S. Flatt, “Lidar measurements taken with a large aperture liquid mirror: 1. The Rayleigh-scatter system,” Appl. Opt. 34, 6925–6936 (1995).
[CrossRef] [PubMed]

E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
[CrossRef]

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

L. Girard, “Etude d’un miroir liquide de 2.5 mètres de diamètre,” Ph.D. thesis (Université Laval, Québec, Canada, 1997).

Hickson, P.

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

Hopkins, G. H.

R. V. Shack, G. H. Hopkins, “The Shack interferometer,” Opt. Eng. 18, 226–228 (1979).
[CrossRef]

Jamar, C. A.

Lalande, R.

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

Mallick, S.

S. Mallick, “Common-path interferometers,” in Optical Shop Testing, D. Malacara, ed. (Wiley, New York, 1978), Chap. 3.

Ninane, N. M.

Poirier, S.

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Poisson, E.

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Roddier, C.

Roddier, F.

Sargoytchev, S.

Sarrow, C. T.

Shack, R. V.

R. V. Shack, G. H. Hopkins, “The Shack interferometer,” Opt. Eng. 18, 226–228 (1979).
[CrossRef]

Sica, R. J.

Szapiel, S.

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

Tremblay, L. M.

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Walker, G. A. H.

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

Wetherell, W. B.

W. B. Wetherell, in Applied Optics and Optical Engineering, Vol. 8, R. R. Shannon, J. Wyant, eds. (Academic, New York, 1980), Chap. 5.

Wuerker, R.

R. Wuerker, “Bistatic LMT lidar alignment,” Opt. Eng. 36, 1421–1424 (1997).
[CrossRef]

Appl. Opt. (3)

Astron. J. (1)

R. Content, E. F. Borra, M. J. Drinkwater, S. Poirier, E. Poisson, M. Beauchemin, E. Boily, A. Gauthier, L. M. Tremblay, “A search for optical flashes and flares with a liquid mirror telescope,” Astron. J. 97, 917–922 (1989).
[CrossRef]

Astrophys. J. (2)

E. F. Borra, R. Content, L. Girard, S. Szapiel, L. M. Tremblay, E. Boily, “Liquid mirrors: optical shop tests and contributions to the technology,” Astrophys. J. 393, 829–847 (1992).
[CrossRef]

E. F. Borra, R. Content, L. Girard, “Optical shop tests of a f/1.2 2.5-meter diameter liquid mirror,” Astrophys. J. 418, 943–946 (1993).
[CrossRef]

Astrophys. J. Lett. (1)

P. Hickson, E. F. Borra, R. Cabanac, R. Content, B. K. Gibson, G. A. H. Walker, “UBC/LAVAL 2.7-meter liquid mirror telescope,” Astrophys. J. Lett. 436, 201–204 (1994).
[CrossRef]

Can. J. Phys. (1)

E. F. Borra, “Liquid mirrors,” Can. J. Phys. 73, 109–125 (1995).
[CrossRef]

J. R. Astron. Soc. Can. (1)

E. F. Borra, “The liquid-mirror telescope as a viable astronomical tool,” J. R. Astron. Soc. Can. 76, 245–256 (1982).

Opt. Eng. (2)

R. V. Shack, G. H. Hopkins, “The Shack interferometer,” Opt. Eng. 18, 226–228 (1979).
[CrossRef]

R. Wuerker, “Bistatic LMT lidar alignment,” Opt. Eng. 36, 1421–1424 (1997).
[CrossRef]

Publ. Astron. Soc. Pac. (1)

E. F. Borra, M. Beauchemin, R. Arsenault, R. Lalande, “Optical-shop testing of liquid mirrors,” Publ. Astron. Soc. Pac. 97, 454–464 (1985).
[CrossRef]

Other (4)

W. B. Wetherell, in Applied Optics and Optical Engineering, Vol. 8, R. R. Shannon, J. Wyant, eds. (Academic, New York, 1980), Chap. 5.

R. Content, “Tests optiques sur un miroir liquide de 1.5 m et développement de la technologie des miroirs liquides,” Ph.D. thesis (Université Laval, Québec, Canada, 1992).

S. Mallick, “Common-path interferometers,” in Optical Shop Testing, D. Malacara, ed. (Wiley, New York, 1978), Chap. 3.

L. Girard, “Etude d’un miroir liquide de 2.5 mètres de diamètre,” Ph.D. thesis (Université Laval, Québec, Canada, 1997).

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Figures (13)

Fig. 1
Fig. 1

Typical scatterplate interferogram of the 2.5-m liquid mirror with a mercury layer of 0.85 mm. The shadow of the hollow central cylinder, used for mercury manipulation, can be seen below the characteristic hot spot of the scatterplate interferogram.

Fig. 2
Fig. 2

Wave front of the mirror with a mercury layer of 0.85 mm. This instantaneous three-dimensional rendering of the surface corresponds to the interferogram shown in Fig. 1.

Fig. 3
Fig. 3

Out-of-focus PSF of the 2.5-m liquid mirror with a 1-arc sec leveling error. The cardioidlike feature at the center can be used to adjust the axis of rotation of the mirror. One can also see radial defects caused by the movement of the liquid over the container.

Fig. 4
Fig. 4

Out-of-focus PSF of the mirror with a mercury layer of 3.0 mm that shows the spiral-shaped defects.

Fig. 5
Fig. 5

Out-of-focus PSF showing the outer region of the mirror with mercury thicknesses of 0.8 and 1.8 mm. The scales are matched so that the edge of the mirror on both images are overlapping. The region from 1.0 to 1.25 m is missing from the image at 1.8 mm. One can see that the spirals extend much farther toward the center of the mirror for the thicker layer.

Fig. 6
Fig. 6

Root-mean-square amplitude of the spiral-shaped defects of two mirrors with 1.5- and 2.5-m diameters. The graph shows that the amplitude is greater for the 2.5-m-diameter mirror with a rim speed 1.67 times faster than the 1.5-m-diameter mirror. It also indicates that the spirals are an edge effect.

Fig. 7
Fig. 7

Sequence of PSF’s used for scattered light measurements. The individual frames are 30 arc sec wide. In view A one can see an unsaturated PSF observed with a 10× microscope objective (2.5 arc sec field of view). In views B, C, and D, we show the PSF directly imaged on the CCD with various levels of saturation. In view D, one sees weak structures (including concentric ring, diffraction cross, ghost images) far from the center of the PSF.

Fig. 8
Fig. 8

Azimuthally averaged PSF’s obtained for three mercury thicknesses on the 2.5-m liquid mirror. They show that scattered light decreases with mercury thickness. The bump at 12.8 arc sec for the curve at 1.8 mm is caused by concentric waves on the mirror.

Fig. 9
Fig. 9

Azimuthally averaged PSF obtained with a 0.5-mm mercury layer for the complete mirror, for the mirror with a diaphragm that excludes the outer 12% of the radius, and for the complete mirror with a 0.41-arc sec leveling error.

Fig. 10
Fig. 10

Encircled energy curves obtained with a 0.5-mm mercury layer for the entire mirror, for the mirror with a diaphragm that excludes the outer 12% of the radius, and for the entire mirror with a 0.41-arc sec leveling error.

Fig. 11
Fig. 11

Azimuthally averaged PSF obtained with a 0.8-mm mercury layer for the mirror under perturbation. Three curves are obtained with the same null lenses alignments: the complete mirror without external perturbation, the mirror with 1.25-arc sec leveling error, and the mirror perturbed with wind of a few kilometers per hour. The reference for a 0.8-mm mercury thickness, with good null lenses alignments, is also shown.

Fig. 12
Fig. 12

Azimuthally averaged rings extracted from PSF’s at various thicknesses of Fig. 8. These rings are caused by concentric waves on the surface of the mirror that act as a phase grating.

Fig. 13
Fig. 13

Out-of-focus PSF’s of the central region of the mirror showing the cardioidlike defect for (A) no leveling error, (B) 1-arc sec leveling error, and (C) 3-arc sec leveling error.

Tables (5)

Tables Icon

Table 1 Wave Front Statistics of Liquid Mirror with 1.5-mm-Thick Mercury Layer

Tables Icon

Table 2 Summary of Wave Front Statistics for Various Mercury Thicknesses

Tables Icon

Table 3 Average Strehl Ratios with Different Diaphragmsa

Tables Icon

Table 4 Wave Front Statistics for Average Wave Fronts for Different Thicknesses and Diaphragms

Tables Icon

Table 5 Wave Front Statistics for Average Wave Fronts for Two Tilt Errors and Two Mercury Thicknesses

Equations (1)

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rms=E/Et1/2λ/4π,

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