Developers guide

19
Figure 2-8 Inner RA limit switches
2.6.3 Tilt sensor
The tilt sensor is used for calibration of the telescope. This is necessary to correctly interpret the
data from the encoders, the encoders can only count the amount of movement or each axis.
This information is meaningless unless used in conjunction with a known reference point.
The tilt sensor has two digital outputs indicating if the telescope is east or north of the zenith. As
shown in Figure 2-14, these outputs are connected to the Macrostation and controlled via the
PMAC device driver.
2.6.4 Macrostation
The MACRO (Motion And Control Ring Optical) – Station is a microprocessor based controller,
manufactured by [ 1 ], used to process the information from the encoders, tilt sensor, limit
switches, and allow software to control the RA and Dec axes.
The PMAC (Programmable Multi Axis Controller, also from [ 1 ]) interface board, installed in
Mistral, is controlled via a Linux device driver
i
, developed by Michael Ashley. The Macrostation is
connected to the PMAC
ii
via a high speed fibre optic network.
The PTCS software system, discussed in Chapter 3.2, in conjunction with the PMAC software is
used to abstract this hardware implementation and provide telescope control.
i
/dev/pmac
ii
A PCI card in Mistral