Harvard-Smithsonian Center for Astrophysics
XRT E2E Test
Day 20050606 Shift B
Test Conductor E. DeLuca
Shift Scientists M. Weber & J. Scott
Best Focus I --- Fine Scan
The result of the Coarse Best Focus scan performed during Shift-A was an estimate of the Best Focus position to be at -750 focus-steps (-460 um) +/- 250 steps. The next step was to perform a focus scan with more precision.
We took images of the Cu-L x-ray source at 41 focus-step positions from -1150 to -350 steps, with step sizes of 20 focus-steps. Each centroid was fitted with a 2D Gaussian, and the widths (i.e., sigmas) were plotted versus focus position. The data was fitted with a 2nd degree polynomial to locate the minimum and determine a Best Focus position.
The plot below displays the data and fit. The Best Focus position for this boresight alignment ("ORIG"; p/y = 0, -1.17') was concluded to be at -770 focus-steps (-472 um), between the minima of the polynomial and data.
