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The Observing Tech (OT) will generally do a Delivered Image Quality (DIQ) measurement early in the night to check and set the telescope optics. However, this does not establish the proper focus for the Hydra instrument. The telescope focus for Hydra must be done while on the target field or while viewing a star with Hydra.
Telescope focus is best done while observing stars with the FOPS, most likely after acquiring the first target field. The focus can be achieved either manually by maximizing the signal into the central fiber of a FOPS probe, or by running an autofocus routine (an OT task).
In conditions of very poor seeing (> 2 to 3 arc-seconds), the telescope can be focused with the Hydra Gripper TV. However, do not rely on this as a good focus for when the seeing is less than 2 arc-seconds.