The total transmission of the spectrograph including
the telescope has been
computed and verified for most of the parts.
Assuming a well functioning telescope
the result is shown in percent in the following
figure
Figure 1. Total transmission over the
wavelength range, varying between 5% to 10%. This is
the design values. This is based on Aluminium coatings on the
collimators, but actually the
mirrors were delivered with silver coating. This means the peak
transmission is higher, but
in the UV a steep fallof takes place around 400 nm.
The spectral format consists of 90 spectral orders,
widely spaced in the blue
end of the spectrum and closer in the red end. Fig.
2 shows the layout on a
30 mm square CCD chip. The free spectral range
(FSR) varies from 22Å
to 119Å at long wavelengths.
Figure 2. The spectral orders of FIES as imaged onto a 30 by 30 mm CCD chip.
Order Central FSR Low High (micron) 69 0.8209 0.0119 0.8149 0.8268 70 0.8092 0.0116 0.8034 0.8149 71 0.7978 0.0112 0.7921 0.8034 72 0.7867 0.0109 0.7812 0.7921 73 0.7759 0.0106 0.7706 0.7812 74 0.7654 0.0103 0.7603 0.7706 75 0.7552 0.0101 0.7502 0.7603 76 0.7453 0.0098 0.7404 0.7502 77 0.7356 0.0096 0.7308 0.7404 78 0.7262 0.0093 0.7215 0.7308 79 0.7170 0.0091 0.7124 0.7215 80 0.7080 0.0089 0.7036 0.7124 81 0.6993 0.0086 0.6950 0.7036 82 0.6907 0.0084 0.6865 0.6950 83 0.6824 0.0082 0.6783 0.6865 84 0.6743 0.0080 0.6703 0.6783 85 0.6664 0.0078 0.6624 0.6703 86 0.6586 0.0077 0.6548 0.6625 87 0.6511 0.0075 0.6473 0.6548 88 0.6437 0.0073 0.6400 0.6473 89 0.6364 0.0072 0.6328 0.6400 90 0.6293 0.0070 0.6259 0.6328 91 0.6224 0.0068 0.6190 0.6259 92 0.6157 0.0067 0.6123 0.6190 93 0.6090 0.0065 0.6058 0.6123 94 0.6026 0.0064 0.5994 0.6058 95 0.5962 0.0063 0.5931 0.5994 96 0.5900 0.0061 0.5869 0.5931 97 0.5839 0.0060 0.5809 0.5869 98 0.5780 0.0059 0.5750 0.5809 99 0.5721 0.0058 0.5692 0.5750 100 0.5664 0.0057 0.5636 0.5692 101 0.5608 0.0056 0.5580 0.5636 102 0.5553 0.0054 0.5526 0.5580 103 0.5499 0.0053 0.5472 0.5526 104 0.5446 0.0052 0.5420 0.5472 105 0.5394 0.0051 0.5369 0.5420 106 0.5344 0.0050 0.5318 0.5369 107 0.5294 0.0049 0.5269 0.5318 108 0.5245 0.0049 0.5220 0.5269 109 0.5196 0.0048 0.5173 0.5220 110 0.5149 0.0047 0.5126 0.5173 111 0.5103 0.0046 0.5080 0.5126 112 0.5057 0.0045 0.5035 0.5080 113 0.5013 0.0044 0.4990 0.5035 114 0.4969 0.0044 0.4947 0.4990 115 0.4925 0.0043 0.4904 0.4947 116 0.4883 0.0042 0.4862 0.4904 117 0.4841 0.0041 0.4820 0.4862 118 0.4800 0.0041 0.4780 0.4820 119 0.4760 0.0040 0.4740 0.4780 120 0.4720 0.0039 0.4700 0.4740 121 0.4681 0.0039 0.4662 0.4700 122 0.4643 0.0038 0.4624 0.4662 123 0.4605 0.0037 0.4586 0.4624 124 0.4568 0.0037 0.4549 0.4586 125 0.4531 0.0036 0.4513 0.4549 126 0.4495 0.0036 0.4478 0.4513 127 0.4460 0.0035 0.4442 0.4478 128 0.4425 0.0035 0.4408 0.4442 129 0.4391 0.0034 0.4374 0.4408 130 0.4357 0.0034 0.4340 0.4374 131 0.4324 0.0033 0.4307 0.4340 132 0.4291 0.0033 0.4275 0.4307 133 0.4259 0.0032 0.4243 0.4275 134 0.4227 0.0032 0.4211 0.4243 135 0.4196 0.0031 0.4180 0.4211 136 0.4165 0.0031 0.4149 0.4180 137 0.4134 0.0030 0.4119 0.4149 138 0.4104 0.0030 0.4090 0.4119 139 0.4075 0.0029 0.4060 0.4090 140 0.4046 0.0029 0.4031 0.4060 141 0.4017 0.0028 0.4003 0.4031 142 0.3989 0.0028 0.3975 0.4003 143 0.3961 0.0028 0.3947 0.3975 144 0.3933 0.0027 0.3920 0.3947 145 0.3906 0.0027 0.3893 0.3920 146 0.3880 0.0027 0.3866 0.3893 147 0.3853 0.0026 0.3840 0.3866 148 0.3827 0.0026 0.3814 0.3840 149 0.3801 0.0026 0.3789 0.3814 150 0.3776 0.0025 0.3764 0.3789 151 0.3751 0.0025 0.3739 0.3764 152 0.3726 0.0025 0.3714 0.3739 153 0.3702 0.0024 0.3690 0.3714 154 0.3678 0.0024 0.3666 0.3690 155 0.3654 0.0024 0.3642 0.3666 156 0.3631 0.0023 0.3619 0.3642 157 0.3608 0.0023 0.3596 0.3619 158 0.3585 0.0023 0.3574 0.3596 159 0.3562 0.0022 0.3551 0.3574