Active Optics Modes of PSF

This page describes the functions of the active optics control buttons on the PSF control sub-GUI.

Secondary Control

The Secondary Control radio buttons select where active optics corrections arriving through the IIF are sent. Primary sends all Zernike terms to the primary mirror. Secondary sends all Zernike terms to the secondary mirror (with limitations for the Rigid - not adaptive - secondary). Split mode sends Z4, Z7, Z8 collimation terms to the secondary hexapod, and the rest of the low-order Zernikes that require a shape change to the primary mirror. Split mode is the default choice. This control is disabled for prime focus observing.

Secondary Active Optics Offload

If large Active Optics corrections are applied to the secondary hexapod, they can result in unwanted binodal astigmatism and tilt in the F/15 focal plane. If the Sec Act Opt Offload is set to yes, then any stepFocus command will cause PSF to offload the accumulated focus and coma corrections from the secondary hexapod to the primary hardpoints. The stepFocus offload function is applied automatically with preset and offset commands (Feb 2009). Warning: Mis-collimation may result in cases where the telescope operator is manually moving the telescope elevation while offloads are pending. Beware of this if you run into the limits of primary mirror travel.

Offload Secondary

The Offload secondary button provides a manual way on the GUI to execute an offload of the secondary active optics corrections to the primary.

Z11/Z22 focus compensation

The Z11/Z22 focus comp button controls whether the focus (Z4) component of a Z11 or Z22 active correction is done by the primary or secondary. The focus compensation reduces the bending forces that are applied to the mirror by generating the focus term by collimation rather than bending. If Z11/Z22 focus comp is set to M2, then the collimation position of the primary will not be updated during active optics corrections. This allows us to avoid the 0.4 arcsec jumps that are associated with an update of the primary hardpoints.

Command for Coma-Free Pointing

adjustPointing side ope tip tilt adds coma-free Pointing Offsets to the PSF input register. This was a new PSF command line command as of 11-May2008. Units of tip (X-direction, or Azimuth) and tilt (Y-direction. or Elevation) are arcsec. As of 24-May-2008 this command has been decommissioned and the same function exists in the "Arbitrator" sub-GUI of PSF. The OPE button selects whether the pointing offsets will be sent to M1 or M2. The offsets are absolute in their application to the Pointing Offset input register, and they are relative as that register sums with the other registers.

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-- JohnHill - 06 Feb 2009