====== Secondary mirror ======

The CSO has a wobbling (chopping) secondary mirror to switch the beam back and forth during observations of compact sources. 
The secondary controller combines an digital servo loop with an automatic tuning algorithm. 
The mirror position is displayed in a window on the remote observing desktop. 

{{secondary.png}}

==== UIP commands ====

To start the secondary wobbler, \\ ''__UIP__> **secondary //throw// //frequency//** ''
  * //throw// is the the beam separation [arcsec]. 
  * For the switching //frequency// [Hz], avoid 1.00 Hz or integer submultiples. Use an odd value instead, such as 0.491 Hz.
  * Tune the secondary mirror wobbler while the telescope is either stationary or sidereal tracking, i. e., not slewing.
To stop the secondary wobbler, \\ ''__UIP__> **secondary /stop ** ''

==== Reference ====

**Controlling a telescope chopping secondary mirror assembly using a signal deconvolution technique ** \\ Houde, M., Holt, L. C., Yoshida, H., Nelson, P. M. \\ 2003 Rev. Sci. Instr. 74, 3802 [[http://adsabs.harvard.edu/abs/2003RScI...74.3802H|ADS]]