Chapter 2- Cassegrain Adapter

Principle

The adapter is the mechanical interface between the telescope and the different instruments to be used in the Cassegrain focus. It contains the optical and mechanical components required for direct and remote observing of: the centerfield, the focusing and the guiding system for the telescope.

The centerfield mirror fixed to a linear actuator, deflects the centerfield 90º through the corresponding TCCD camera. Furthermore, the field passes either the large or small field onto the 90º plane mirror which deflects the field towards the TCCD.

The adapter is mounted directly on a large precision roller bearing bolted onto the reference plate, on the rear side of the mirror cell. The local control electronics is installed in one of the four racks inside the Cassegrain cage. There is also a TCCD camera for observation of the center field and the guide field. In automatic mode the adapter is remotely operated by the telescope control system.

The rotator is a large precision roller bearing where the outer bearing ring is bolted onto the reference plate on the rear side of the mirror cell, and the inner bearing ring onto the adapter housing. The inner bearing ring is provided with internal gear teeth and is turned by 3 parallel driven DC motor up to +/-182º from South direction. The rotation is limited by 2 electrical and mechanical stops. The angular position is read by an absolute encoder with a resolution of 0,036º while the reading accuracy of position is +/- 0,1º.

In November 23, 2001 a Slit Viewer modification was made in order to fit Adaptor to HARPS requirements

The adapter electronic control system is described in the 3p6 Team page. A PDF version of the Adapter Block Diagram is in AdapterFunctions.pdf

Preliminary Adapter Documentation (Hans Attersjoe)

Send Comments to: Agustin Macchino Last update: July 18, 2001