Table 1
ELT f/5 Design Parameters Optimized Across a
6 arc min FOVa
Mi
 Curvature Radius (mm)
 Thickness from Mi to Mi + 1
 Optical Clear Aperture (mm)
 Hole (mm)
 Conic
 Figure Deviation (Df) from BFS


M1  71324.73  37900.000  25000  5200  0.000  Spherical 
M2  +10171.61  +2788.788  2060  600  18.470  Prolate ellipsoid, Df = 0.73 mm 
M3  5025.15  8911.525  2690  95  1.413  Hyperboloid, Df = 1.12 mm 
M4  +6311.22  +5690.573  4340  280  0.291  Oblate ellipsoid, Df = 0.86 mm 
M5  +13372.57  5797.960  1180  240  0.000  Aspherical, Df = 1.50 mm 
FP  1235.43   109.1  —  0.000  Spherical 
M5 
A = 4.25183 × 10
^{11
} 
B = 6.12178 × 10
^{18
} 
C = 1.15078 × 10
^{23
} 

D = 1.42958 × 10
^{29
} 
E = 2.18073 × 10
^{36
} 
F = 7.81065 × 10
^{42
} 
FP is the focal plane, and the plate scale is
S =
1.65 arc sec/mm.
A,
B,
C,
D,
E, and
F
are the fourth, sixth, eighth, tenth, twelfth, and
fourteenthorder deformation coefficients, respectively, for aspherical
surface M5.
Table 2
ELT f/5 Compact Design Parameters Optimized
Across a 3 arc min FOVa
Mi
 Curvature Radius (mm)
 Thickness from Mi to Mi + 1
 Optical Clear Aperture (mm)
 Hole (mm)
 Conic
 Figure Deviation (Df) from BFS


M1  71324.73  37900.000  25000  5200  0.000  Spherical 
M2  +9426.44  +2751.595  2060  600  5.882  Prolate ellipsoid, Df = 0.27 mm 
M3  4758.10  6657.583  2690  95  1.980  Hyperboloid, Df = 1.78 mm 
M4  +3925.87  +3397.270  2680  260  0.178  Oblate ellipsoid, Df = 0.32 mm 
M5  +8361.70  4171.702  840  120  0.000  Aspherical, Df = 0.88 mm 
FP  1147.50  —  54.55  —  0.000  Spherical 
M5 
A = 9.67111 × 10
^{11
} 
B = 3.83967 × 10
^{17
} 
C = 8.53434 × 10
^{23
} 

D = 2.02072 × 10
^{28
} 
E = 8.78626 × 10
^{34
} 
F = 1.17403 × 10
^{39
} 
FP is the focal plane and the plate scale is
S =
1.65 arc sec/mm.
A,
B,
C,
D,
E, and
F
are the fourth, sixth, eighth, tenth, twelfth, and
fourteenthorder deformation coefficients, respectively, for aspherical
surface M5.
Table 3
ELT f/5 TwoAxis TwoMirror Design
Parameters Optimized Across a 3 arc min
FOVa
Mi
 Curvature Radius (mm)
 Thickness From Mi to Mi + 1
 Optical Clear Aperture (mm)
 Conic
 Figure Deviation (Df) from BFS


M1  71324.73  35100.000  25000  0.000  Spherical 
F1  Flat  +803.517  Prime focus  —  Flat 
M2  7961.34  4233.515  620  36.84  Aspherical, Df = 0.025 mm 
M3  +6888.43  +14784.875  2960  1.413  Aspherical, Df = 2.33 mm 
FP  +4791.78  —  109.09  0.000  Spherical 
M2 
A = 1.73400 × 10
^{11
} 
B = 2.14090 × 10
^{16
} 
C = 1.2962 × 10
^{20
}  
D = 3.46076 × 10
^{24
} 
M3 
A = 1.32963 × 10
^{12
} 
B = 3.94137 × 10
^{20
} 
C = 8.99992 × 10
^{28
}  
D = T2.37205 × 10
^{34
} 
FP is the focal plane and the plate scale is
S =
1.65 arc sec/mm.
A,
B,
C, and
D are
the fourth, sixth, eighth, and tenthorder deformation coefficients,
respectively, for the M2 and M3 aspherical surfaces.
Table 4
ELT f/5 SingleAxis ThreeMirror Design
Parameters Optimized across a 6 arc min
FOVa
Mi
 Curvature Radius (mm)
 Thickness from Mi to Mi + 1
 Optical Clear Aperture (mm)
 Conic
 Figure Deviation (Df) from BFS


M1  71000.00  37801.612  25000  0.000  Spherical 
M2  +6909.69  +2880.279  2200  1.802  Aspherical, Df = 0.105 mm 
M3  5408.37  2956.237  2400  1.990  Aspherical, Df = 2.83 mm 
M4  2318.54  +1201.699  560  3.716  Prolate ellipsoid, D = 0.060 mm 
F1  Flat  1202.006  560 (350 OBS)  —  Flat 
FP  +5107.41  —  218.18  0.000  Spherical 
M2 
A = 9.43074 × 10
^{13
} 
B = 1.67840 × 10
^{20
}  
C = 1.674180 × 10
^{27
} 
M3 
A = 6.91822 × 10
^{12
} 
B = 2.78349 × 10
^{19
}  
C =5.23827 × 10
^{27
} 
FP is the focal plane and the plate scale is
S =
1.65 arc sec/mm.
A,
B, and
C are the
fourth, sixth, and eighthorder deformation coefficients,
respectively, for the M2 and M3 aspherical surfaces. OBS is the
obscuration diameter.
Table 5
Possible Corrector Designs for f/5
ELTa
Design
 FOV (arc min)

D
80 (arc sec)
 Maximum Area Obscuration (%)
 Corrector Cylindrical Box (m × m)
 Stronger Df for Aspherical Mirror (mm)


1 × 4  6.0  0.09  8.5  4.4 × 9.0  1.18 M with Df = 1.50 
Short  3.0  0.06  7.0  2.8 × 6.7  0.84 M with Df = 0.88 
2 × 2  3.0  0.09  8.0  3.0 × 4.5  2.96 M with Df = 2.33 
1 × 3  6.0  0.03  9.0  2.5 × 3.0  2.40 M with Df = 2.83 
D80 is the circle diameter with 80% encircled energy,
Df is the figure deviation from the BFS. 1 × 4 indicates
singleaxis fourmirror corrector.