Zeroth-order 1D FWHM vs Time, April 4, '00

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The FWHM of the 1D projection of the zeroth-order PSF was measured for 8 additional point-source HETGS observations and continues to look stable over > 200 days; see the plot below. This is in agreement with the CXC Cal analysis of the ACIS-S Plate Focus taken on March 23, 2000 which also shows no significant change in focus location.

The 1D FWHM was measured using the "streak" events as described in Measured and Modelled zeroth-order 1D projections.

[ also available in a postscript version ]

Software and Data File

The data were processed with HAK software and ISIS as described at Measured and Modelled zeroth-order 1D projections using an updated version of the ISIS scripts. The ISIS fit results were then manually entered into an rdb file which an IDL procedure read to create the plot. These components are given here for reference:

Please send any comments to Dan Dewey at

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