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TECHNICAL NOTES ON THE OPTICAL CONFIGURATION OF VST INCLUDING AN ADC Prepared by : D. Ferruzzi, G. Marra To the attention of : D. Mancini

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Introduction

In the study of ADC to be inserted in the optical design of VST, we considered two possible solutions. In one of them the ADC had flat entrance and exit surfaces and in the other one, the external surfaces were curved. In the next sections the two systems are described. It would be necessary to contact Zeiss to know as soon as possible if both solutions are reliable and to have indications about costs of manufacturing and handling.

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ADC with entrance and exit curved surfaces

The ADC has curved entrance and exit surfaces and is inserted between the third lens and the filter. The triplet is the same of the last configuration sent to Zeiss, while the rays of curvature and the conics of the mirrors were modified. In Table 1-1 the ADC optical data are reported. In Figure 2-1 the camera, ADC, filter and dewar window layout is reported. In Figures 2-2, 2-3, 2-4 spot diagrams corresponding to the minimum dispersion configuration at zenith, maximum dispersion at 60° and ADC compensation at 60° are shown.

Surface 1 2 3 4 5

Material UBK7 LLF6 air UBK7 LLF6

Ray of curvature 1584.9 mm infinity infinity -4893.87

Prism angle

Thickness 16 mm 14 mm 3 mm 16 mm 14 mm

Diameter 352.948 353.420 351.866 351.912 352.687 mm mm mm mm mm

2.8 deg

-2.8 deg

Table. 2-1 Optical data for the ADC with curved entrance and exit surfaces

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Figure.2-1 Camera and ADC with curved surfaces in the maximum dispersion configuration

Figure.2-2 Spot corresponding to the configuration of minimum dispersion at zenith
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Figure.2-3 Spot corresponding to maximum dispersion at 60°

Figure.2-4 Spot corresponding to the ADC compensation at 60°

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ADC with flat entrance and exit surfaces configuration

This design has an ADC with all flat surfaces. The lenses of the camera were reoptimized together with the mirrors parameters respect to the previous solution. The rays of curvatures were normalized to Din Tables. In Table 3-1 the ADC optical data are reported. In Figure 3-1 the camera, ADC, filter and dewar window layout is reported. In Figures 3-2, 3-3, 3-4 spot diagrams corresponding to the minimum dispersion configuration at zenith, maximum dispersion at 60° and ADC compensation at 60° are shown.

Surface 1 2 3 4 5

Material UBK7 LLF6 air UBK7 LLF6

Ray of curvature Infinity Infinity Infinity Infinity

Prism angle

Thickness 15 mm 15 mm 3 mm 15 mm 15 mm

Diameter 352.336 mm 353.13 mm 354.28 mm 354.336 mm 354.89 mm

3 deg

-3 deg

Table. 3-1 Optical data for the ADC with curved entrance and exit surfaces

Figure. 3-1 Camera and ADC with flat surfaces in the minimum dispersion configuration

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Figure. 3-2 Spot corresponding to the minimum dispersion at the zenith angle with ADC

Figur 3-3 Spot corresponding to the maximum dispersion at 60°

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Figure. 3-4 Spot corresponding to the ADC compensation at 60°

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