Observers who expect to make use of extended hours should contact their support scientist well in advance of the run to allow us to take this into account whenever possible in planning our maintenance schedules. Note that during the daytime hours the pointing is frequently extremely poor due to very high refraction noise and highly variable opacity (given respectively by the phase monitor and CSO tau meter and displayed in near real-time on the telescope screen). The amount of extended time is monitored as part of our procedures to determine cost effectiveness.

The switch between first and second shift is deemed to take place at 1330 hours if both shifts wish to make use of the daytime.

Director JCMT