A review is made of present possibilities in the design of large refracting telescope objectives intended for visual or detector-aided studies of the planets from ground-based observatories. The great progress in the technology of optical glass achieved during the past several decades makes it worthwhile now for one to re-examine the question of whether the performance of any large refractor made in the future can be improved. On the whole the answer is affirmative but with reservations as to the importance of such an accomplishment in modern astronomy. A comprehensive discussion is given of the optical and environmental problems encountered, and several examples are given to demonstrate the degree of improvement to be expected from both semiapochromatic and fully apochromatic objectives.*
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
You do not have subscription access to this journal. Article tables are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Unfavorable bubble quality.
With bubbles.
The designation EBA in translation means much reduced bubble content. SK and SSK glasses not having the EBA designation do have numerous bubbles.
The designation FA means with reduced coloration.
Table II
Maximum Volume List for Selected Types as of November 1961
Glass type
Maximum volume (liters)
Maximum diameter obtainable for 3 given thicknesses
60 mm
80 mm
115 mm
PSK-1
50
102.5 cm
89.0 cm
74.5 cm
BK-7
100
146.0
125.5
105.0
ZK-2
75
125.0
109.0
91.5
BaK-2
75
125.0
109.0
91.5
SK-2
50
102.5
89.0
74.5
SK-11
50
102.5
89.0
74.5
BaLF-3
50
102.5
89.0
74.5
BaLF-6
50
102.5
89.0
74.5
F-2
65
118.0
102.5
85.0
KzF-5
50
102.5
89.0
74.5
KzFS-2
25
72.5
63.0
52.5
KzFS-3
25
72.5
63.0
52.5
KzFS-4
25
72.5
63.0
52.5
Table III
Color Curves of Selected Combinations
Wavelength designation
Standard achromat BK-7 F-4
Doublet apochromat ZK-2 KzF-5
Triplet apochromat PSK-1 KzFS-2 PSK-1
Triplet apochromat BK-7 KzF-BaLF-6
Triplet apochromat BK-7 CaF2 K-10
4047 (h)
57.4
21.1
24.3
20.3
8.1
4358 (g)
25.5
7.7
9.3
8.2
1.5
4800 (F′)
6.0
4.4
−0.4
0.7
4861 (F)
5.0
2.6
−0.1
2.0
−0.2
5461 (e)
−0.8
0.0
−0.8
−0.3
−0.8
5876 (d)
−0.6
−1.0
−0.4
−1.0
5893 (D)
0.1
−0.8
0.1
0.5
0.4
6438 (C)
2.9
0.8
−1.0
0.7
6563 (C)
3.7
1.9
0.0
1.5
−0.1
7682 (A′)
11.5
2.4
0.8
1.3
−0.1
10,140
31.3
4.8
6.9
Table IV
Color Curves in Terms of Focal Displacement
Wavelength designation
Standard achromat BK-7 F-4
Doublet apochromat ZK-2 KzF-5
Triplet apochromat PSK-1 KzFS-2 PSK-1
Triplet apochromat BK-7 KzF-5 BaLF-6
Triplet apochromat BK-7 CaF2 K-10
Schupmann ZK-7 (with PKS-1 and KzFS-2)
4047 (h)
0.004590
0.001687
0.001944
0.001620
0.000649
0.000029
4358 (g)
0.002197
0.000660
0.000801
0.000703
0.000126
0.000000
4800 (F′)
0.000564
0.000409
−0.000035
0.000066
−0.000010
4861 (F)
0.000484
0.000249
−0.000005
0.000191
−0.000016
−0.000011
5461 (e)
−0.000086
0.000000
−0.000090
−0.000028
−0.000086
−0.000011
5876 (d)
−0.000074
−0.000115
−0.000047
−0.000116
−0.000007
5893 (D)
0.000009
−0.000096
0.000008
0.000053
0.000048
−0.000008
6438 (C′)
0.000362
0.000098
−0.000127
0.000085
−0.000002
6563 (C)
0.000483
0.000249
−0.000006
0.000191
−0.000016
0.000000
7682 (A′)
0.001742
0.000358
0.000119
0.000191
−0.000016
0.000009
10140
0.006269
0.000962
0.001383
Table V
Comparison of Selected Glass Combinations in Terms of Focal Ratio for Similar Performance
Wavelength designation
Standard achromat BK-7 F-4 f/163
Doublet apochromat ZK-2 KzF-5 f/H2
Triplet apochromat PSK-1 KzFS-2 PSK-1 f/62
Triplet apochromat BK-7 KzF-5 BaLF-6 f/109
Triplet apochromat BK-7 CaF2 K-10 f/106
Schupmann ZK-7 (with PKS-1 and KzFS-2) f/20
4800 (F′)
1.0
1.1
−0.1
0.2
0.0
4861 (F)
0.8
0.7
−0.2
0.5
0.0
0.0
5461 (e)
−0.1
0.1
−0.2
0.0
−0.1
0.0
5876 (d)
−0.1
−0.1
0.0
−0.2
0.0
5893 (D)
0.1
−0.1
0.2
0.1
0.1
0.0
6438 (C′)
0.5
0.3
−0.3
0.2
0.0
6563 (C)
0.6
0.5
−0.1
0.4
0.0
0.0
Table VIa
Transmission Data for a 25-cm Thickness (Surface Reflections Excluded)
Wavelength
BK-7 (mean value)
ZK-2 (melt Z 10019)
3650
0.70
0.749
4000
0.88
0.920
4047
0.89
0.925
4358
0.91
0.902
5461
0.95
0.949
5780
0.95
0.947
5820
0.95
0.943
7000
0.95
0.952
Table VIb
Transmission Data for a 10-cm Thickness (Surface Reflections Excluded)
Wavelength
PSK-1
BK-7
ZK-2
BaK-2
SK-11 (mean)
BaLF-3
BaLF-6
4358
0.931
0.952
0.960
4861
0.977
5000
0.966
0.983
0.978
5200
0.983
5461
0.974
0.983
0.979
0.985
0.972
0.987
0.984
5780
0.970
0.983
0.978
0.982
0.970
0.984
0.980
5820
0.977
6000
0.983
6200
0.963
0.983
0.978
0.967
0.975
0.980
7000
0.965
0.983
0.981
0.966
0.975
0.980
7600
0.980
Wavelength
SF-2
SF-4
SF-5
SF-6 FA
KzF-5
KzFS-2
KzFS-3
KzFS-4(mean)
4358
0.74
0.808
0.918
4861
0.954
5000
0.970
0.981
0.985
0.964
5200
0.974
0.981
5461
0.989
0.989
0.992
0.987
0.968
0.979
0.984
0.968
5780
0.990
0.988
0.992
0.988
0.968
0.974
0.977
0.960
6000
0.983
0.981
6200
0.985
0.965
0.971
0.954
6600
0.980
0.981
7000
0.992
0.993
0.988
0.954
0.959
0.945
7600
0.996
0.995
7800
0.993
8000
0.994
0.995
8200
0.992
Table VII
Transverse Intercepts in the Gaussian Focal Plane for a 15-cm f/10 Fluorite Triplet (with Aspheric Figuring)
Unfavorable bubble quality.
With bubbles.
The designation EBA in translation means much reduced bubble content. SK and SSK glasses not having the EBA designation do have numerous bubbles.
The designation FA means with reduced coloration.
Table II
Maximum Volume List for Selected Types as of November 1961
Glass type
Maximum volume (liters)
Maximum diameter obtainable for 3 given thicknesses
60 mm
80 mm
115 mm
PSK-1
50
102.5 cm
89.0 cm
74.5 cm
BK-7
100
146.0
125.5
105.0
ZK-2
75
125.0
109.0
91.5
BaK-2
75
125.0
109.0
91.5
SK-2
50
102.5
89.0
74.5
SK-11
50
102.5
89.0
74.5
BaLF-3
50
102.5
89.0
74.5
BaLF-6
50
102.5
89.0
74.5
F-2
65
118.0
102.5
85.0
KzF-5
50
102.5
89.0
74.5
KzFS-2
25
72.5
63.0
52.5
KzFS-3
25
72.5
63.0
52.5
KzFS-4
25
72.5
63.0
52.5
Table III
Color Curves of Selected Combinations
Wavelength designation
Standard achromat BK-7 F-4
Doublet apochromat ZK-2 KzF-5
Triplet apochromat PSK-1 KzFS-2 PSK-1
Triplet apochromat BK-7 KzF-BaLF-6
Triplet apochromat BK-7 CaF2 K-10
4047 (h)
57.4
21.1
24.3
20.3
8.1
4358 (g)
25.5
7.7
9.3
8.2
1.5
4800 (F′)
6.0
4.4
−0.4
0.7
4861 (F)
5.0
2.6
−0.1
2.0
−0.2
5461 (e)
−0.8
0.0
−0.8
−0.3
−0.8
5876 (d)
−0.6
−1.0
−0.4
−1.0
5893 (D)
0.1
−0.8
0.1
0.5
0.4
6438 (C)
2.9
0.8
−1.0
0.7
6563 (C)
3.7
1.9
0.0
1.5
−0.1
7682 (A′)
11.5
2.4
0.8
1.3
−0.1
10,140
31.3
4.8
6.9
Table IV
Color Curves in Terms of Focal Displacement
Wavelength designation
Standard achromat BK-7 F-4
Doublet apochromat ZK-2 KzF-5
Triplet apochromat PSK-1 KzFS-2 PSK-1
Triplet apochromat BK-7 KzF-5 BaLF-6
Triplet apochromat BK-7 CaF2 K-10
Schupmann ZK-7 (with PKS-1 and KzFS-2)
4047 (h)
0.004590
0.001687
0.001944
0.001620
0.000649
0.000029
4358 (g)
0.002197
0.000660
0.000801
0.000703
0.000126
0.000000
4800 (F′)
0.000564
0.000409
−0.000035
0.000066
−0.000010
4861 (F)
0.000484
0.000249
−0.000005
0.000191
−0.000016
−0.000011
5461 (e)
−0.000086
0.000000
−0.000090
−0.000028
−0.000086
−0.000011
5876 (d)
−0.000074
−0.000115
−0.000047
−0.000116
−0.000007
5893 (D)
0.000009
−0.000096
0.000008
0.000053
0.000048
−0.000008
6438 (C′)
0.000362
0.000098
−0.000127
0.000085
−0.000002
6563 (C)
0.000483
0.000249
−0.000006
0.000191
−0.000016
0.000000
7682 (A′)
0.001742
0.000358
0.000119
0.000191
−0.000016
0.000009
10140
0.006269
0.000962
0.001383
Table V
Comparison of Selected Glass Combinations in Terms of Focal Ratio for Similar Performance
Wavelength designation
Standard achromat BK-7 F-4 f/163
Doublet apochromat ZK-2 KzF-5 f/H2
Triplet apochromat PSK-1 KzFS-2 PSK-1 f/62
Triplet apochromat BK-7 KzF-5 BaLF-6 f/109
Triplet apochromat BK-7 CaF2 K-10 f/106
Schupmann ZK-7 (with PKS-1 and KzFS-2) f/20
4800 (F′)
1.0
1.1
−0.1
0.2
0.0
4861 (F)
0.8
0.7
−0.2
0.5
0.0
0.0
5461 (e)
−0.1
0.1
−0.2
0.0
−0.1
0.0
5876 (d)
−0.1
−0.1
0.0
−0.2
0.0
5893 (D)
0.1
−0.1
0.2
0.1
0.1
0.0
6438 (C′)
0.5
0.3
−0.3
0.2
0.0
6563 (C)
0.6
0.5
−0.1
0.4
0.0
0.0
Table VIa
Transmission Data for a 25-cm Thickness (Surface Reflections Excluded)
Wavelength
BK-7 (mean value)
ZK-2 (melt Z 10019)
3650
0.70
0.749
4000
0.88
0.920
4047
0.89
0.925
4358
0.91
0.902
5461
0.95
0.949
5780
0.95
0.947
5820
0.95
0.943
7000
0.95
0.952
Table VIb
Transmission Data for a 10-cm Thickness (Surface Reflections Excluded)
Wavelength
PSK-1
BK-7
ZK-2
BaK-2
SK-11 (mean)
BaLF-3
BaLF-6
4358
0.931
0.952
0.960
4861
0.977
5000
0.966
0.983
0.978
5200
0.983
5461
0.974
0.983
0.979
0.985
0.972
0.987
0.984
5780
0.970
0.983
0.978
0.982
0.970
0.984
0.980
5820
0.977
6000
0.983
6200
0.963
0.983
0.978
0.967
0.975
0.980
7000
0.965
0.983
0.981
0.966
0.975
0.980
7600
0.980
Wavelength
SF-2
SF-4
SF-5
SF-6 FA
KzF-5
KzFS-2
KzFS-3
KzFS-4(mean)
4358
0.74
0.808
0.918
4861
0.954
5000
0.970
0.981
0.985
0.964
5200
0.974
0.981
5461
0.989
0.989
0.992
0.987
0.968
0.979
0.984
0.968
5780
0.990
0.988
0.992
0.988
0.968
0.974
0.977
0.960
6000
0.983
0.981
6200
0.985
0.965
0.971
0.954
6600
0.980
0.981
7000
0.992
0.993
0.988
0.954
0.959
0.945
7600
0.996
0.995
7800
0.993
8000
0.994
0.995
8200
0.992
Table VII
Transverse Intercepts in the Gaussian Focal Plane for a 15-cm f/10 Fluorite Triplet (with Aspheric Figuring)