next up previous contents index
Next: Spectrographs Up: Instrumentation at the Previous: Large external memory

The Two-degree Field project

In 1990 the AAT Board agreed to proceed with the construction of a major new instrument for the AAT. The Two-degree Field (2dF) project is currently in its shake down phase.

This project builds on the successful optical fibres work undertaken by the Observatory over the last decade. Based on the existing AUTOFIB, the 2dF will provide a survey facility, with a two degree field of view, at the prime focus of the AAT. The 400 optical fibres used in the instrument will feed several dedicated fibre spectrographs. The concept depends upon the Ritchey-Chrétien design of the AAT, which makes it feasible to have a 2° diameter corrected field at the prime focus.

A prime focus corrector gives the AAT the capability of producing aberration corrected images over a full 2 degree field of view. This four component corrector, complete with atmospheric dispersion compensator, (see Figure 4.1) is the heart of a 400 fibre spectroscopic survey facility known as the 2dF. The other main components of the system are the fibre positioner, the two dedicated fibre spectrographs and the 2dF aquisition and data reduction software.

The fibre positioner accommodates 400 fibres, feeding two separate spectrographs. Fibre positioning, at the accuracy required, takes time so the system is double buffered, allowing data acquisition to take place on the active plate while reconfiguration is done on the other. Reconfiguration is performed using a robotic gripper head mounted on an X Y gantry. A tumbler shifts the newly configured field into position when required.

The spectrographs are designed to provide high throughput over the range of 350nm to 1um.   Software is being produced in-house, in C, on a distributed VMS/UNIX/VME based sytem. The software interfaces use TCL/TK and the environment is the AAO developed DRAMA system.

For further details see the 2dF Home Page , which also contains a User Manual.

 
Figure 4.1: Optical system for the 2dF


Figure 4.2: 2dF top end



This Page Last updated: 18 February 1997 by Chris Tinney