Update Jan 10 2024: The issue was resolved during SSD23 and the AGw patrol field is back to the nominal area described in the LUCI pages (here).  The problem was traced to the camera cable, where a couple of wires were broken but the disconnection only manifested at certain positions in the patrol field.  

Update June 30:  Despite yesterday’s additional inspection, testing, and re-seating an accessible cable for the guide camera, last night we had another dropout of the guide camera right at the limit established in March.  For normal observing I would still recommend avoiding guide stars at all dither positions landing in the red shaded area in the plot. When planning your observations in the OT, use the inflection point at left (marked in the diagram below) where the theta stage limit and the 5.5 arcminute Gregorian focal plane radius intersect as a reference.

When observing, the symptom of encountering this problem is a “no guide star found” error when otherwise it should be there.  The only remedy is to select a better-positioned guide star and start the observations over.

March 2023:  We have identified a position-dependent electrical problem in the AGw1 (LUCI1) off-axis guider camera.  It is most likely in the cable between the guider CCD and the controller box.  This cable is inaccessible on the telescope, so until we can schedule a repair it will be necessary to ensure that any off-axis guide stars (and all the dither positions used!) avoid moving into the upper third of the AGw patrol field (see below).

When planning your observations in the OT, use the inflection point at left (marked in the diagram below) where the theta stage limit and the 5.5 arcminute Gregorian focal plane radius intersect.  If you have any questions please send them to us at scienceops@lbto.org.