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Telescopes Branch
HST Focus

The data from the Sep 9th visit of CAL10752 (HST Optical Monitoring) have been analyzed. Results of phase retrieval on stellar targets in ACS/HRC & WFPC2/PC in parallel give good agreement with the mean of HRC measurements over the orbit. HRC values indicated +0.6 microns (@ secondary mirror), while the PC mean was ~ -0.6 microns. For reference, 1 micron of Secondary Mirror despace produces 6 nanometers of rms wavefront error, or ~1/100 wave in V-band.

This visit, along with the previous, illustrate that the July 31 Secondary Mirror adjustment was successful in restoring sharp focus; the mean of the last two HRC visits being 0.02 microns. See plot.