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This program is the Cycle 29 implementation of the HST Optical Monitoring Program. The 6 orbits comprising this proposal will utilize ACS (Wide Field channel) and WFC3 (UVIS channel) to observe stellar cluster members in parallel with multiple exposures over an orbit. Phase retrieval performed on the PSF in each image will be used to measure primarily focus comma with the ability to explore apparent coma comma astigmatism comma and third order spherical changes in WFC3. The goals of this program are todoublePoint 1. monitor the overall OTA focal length for the purposes of maintaining focus within science tolerances. 2. determine focus offset between the imagers and identify any SI-specific focus behavior and dependencies. Starting with cycle 25 comma POSTARGY = -41 is used to make the UVIS detector rotate about its center instead of about the center of the chip UVIS1 as ORIENT changes over the course of the year. The resulting smaller area covered by UVIS has been matched to a dense part of the cluster to ensure a resonably large number of bright stars on UVIS in each visit. The combination of the new target position (NGC-188-DENSE) and POSTARGY has moved the center of rotation by (+46 arcsec comma -23 arcsec) in (RA comma Dec). The density of bright stars in the annulus sampled by the ACS-WFC parallel exposures has also been checked. Where needed comma the intervals between visits have been adjusted to ensure that each chip of each detector will cover an adequate number of stars.