Large Telescope Mount

The mount uses an Alt-Az design that can also be realized as equatorial fork mount providing the needed inclination to the heaven's pole. Note, that the equatorial option is not suitable for telescopes above 1m due to weight limiting.

Alt-az design

The great advantage of the Alt-az design telescope mount is the fork that can be made much smaller and therefore the total telescope weight is decreased. We use a by today Direct Drive System. The mount is optimized by means of FEM calculations. The measured eigen-frequency is about 15Hz. A high eigen frequency is desirably for a telescope because it means than the telescope is very rigidly. We can guarantee at least 10 Hz.

To find out if the telescope is in equilibrium the drive can be de-coupled. Then counterweights can be added to put the telescope in equilibrium. We use Torque motors. The electronic that drives the Torquemotors uses a PID-controller that is specially modified to make a very smooth tracking even at very low frequencies.

Another safety method we use is to compare the Renishaw Absolut Encoders position with the Motor-Encoder position. If the software detects a certain difference the telescope is shut down because the telescope will probably have hit some resistance.

These Encoders are directly attached to the telescope axis and are the same that are used in the big-size professional ESO-telescopes. Encoders are used to make realtime-corrections of  wind-load.