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Prime Focus Corrector System
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The following image shows an extract from the WEAVE instrument block diagram which depicts the sub-assemblies (blue) that constitute the Two-degree Prime Focus system (yellow). These sub-assemblies will be delivered as part of this system however the control aspects of the moving mechanisms are described in Observatory Control System. |
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The Two-degree Prime Focus system (PRI) is composed of:
The following pictures represents the system. The Fibre Positioner which is for completeness does not form part of this system. |
WEAVE Prime Focus Assembly (WPFA)
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The optical system for the WEAVE Prime Focus Corrector is composed of six lenses made of different materials with specific characteristics. . The purpose of the WEAVE Prime Focus Corrector (PFC) is to correct for the (geometrical) optical aberrations in the two-degree field-of-view (WHT’s primary mirror is parabolic). It also comprises an Atmospheric Dispersion Corrector (ADC), performed by two pairs of counter-rotating air-separated doublets, to compensate for atmospheric dispersion (chromatism) whilst the telescope is moving in elevation. The optical layout for the PFC design is shown below: |
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The characteristics of the optical design are:
The performance of the optical design is such that 80% of the energy is encircled within 1” or 56um (~50% contribution from the optical design & ~50% contribution from the manufacturing tolerances). This image quality is met for these conditions, simultaneously:
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A model of the proposed PFC is shown beneath. The six lenses are held within this structure which has a physical interface with the Central Can. |
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The Central Can (already manufactured) is attached to the vanes which are attached to the Focal Translation System. In this photo the dummy PFC is inserted into the Central Can. |
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