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Guiding Options

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Phoenix does not contain an on-instrument wavefront sensor and therefore the fast tip-tilt guiding, which is mandatory for all observations with Gemini, requires guide stars to be acquired using the facility peripheral wavefront sensor (usually PWFS-2).

The small size of the science field of view allows a smaller inner radius of the WFS patrol field than for many Gemini instruments, and stars can be selected for PWFS-2 down to 4.5 arcmin from the science target. The outer limit for PWFS2 guide stars can be displayed on the OT position editor and is discussed here. For guide star separations close to the minimum, it is a good idea to use the OT position editor to check that the probe arm does not vignette the science field of view.

It is usually best to pick the brightest guide star available within the WFS patrol field. Be aware of the impact of your requested observing constraints (cloud cover, image quality) will have on the observed brightness of your selected guide star. Guide stars that are adequate in good conditions may not be suitable in poor IQ or cloudy conditions.