Switching between using LRIS with the Cass ADC (LRIS-ADC mode) and without ("plain LRIS" mode) is cumbersome and time consuming to our summit staff. Since the majority of observing programs will benefit from the improved image quality and slit throughput delivered by the Cass ADC, we encourage LRIS observers to use LRIS-ADC instead of LRIS. Hence, Keck has decided to offer the plan LRIS option only to those who specifically request and can provide compelling scientific justification, such as:

• performing polarimetry;
• re-using old LRIS slitmasks designed for non-ADC mode;
• obtaining precision imaging for which loss of throughput and ghosting induced by Cass ADC are unacceptable.

Since most observers will use LRIS-ADC mode, it is highly likely that non-ADC observers will be awarded time at the start or end of the LRIS run, rather than in the middle.