Beam Splitters

Just below the ADC is a turret wheel containing the beam splitters that send part of the light to the AGW unit for acquisition, guiding, and wavefront sensing.  There are 5 different beam splitters for observing, and the choice depends on the brightness of the target and the cross dispersers to be used.   PFU beam splitter is selected automatically according to the brightness of the target and cross-disperser used during OB generation.

• BS1 – grey – 2% of science light reflected to guider
• BS2, BS3  – 10% of science light reflected to guider
• BS4, BS5  – 50% of science light reflected to guider

The Beamsplitters are optimized for the red cross dispersers and are automatically selected in the PEPSI Observing Block when the cross disperser is selected.  The Beamsplitter for the appropriate magnitude is selected when generating the scripts.

Optimal configurations for Beam splitters are:

Vmag Range	CD IV	CD V	CD VI
0-14	BS#1	BS#1	BS#1
14-17	BS#2	BS#2	BS#3
17-20	BS#4	BS#4	BS#5