When using pickoff mirrors, the location of the guide star depends on the design software used to define a slitmask. There are two software packages used to design slitmasks for LRIS: Because the Pointing Origins are updated more frequently than the design software, the coordinates of the guide star location specified by the design software is out of date. To determine the guide star location please review the information below.

Autoslit

The Autoslit software allows you to offset the target field and guide star relative to the center position as specified in the coordinate input file. Offsets are applied using the "C" option.

UCSCLRIS

The UCSCLRIS software package also allows you to specify the location of a guide star on the pickoff mirror.During a recent engineering night we re-measured the offset between the predicted and actual location of stars on the guider. Until further notice, observers should apply the following offset to their pickoff star coordinates: