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At some off-axis locations outside the standard spectroscopy region, not enough calibration data exist to create a reliable HRC-S degap map. To fix this problem, degap coefficients from the nearest well-calibrated row have been extrapolated into the uncalibrated region.
The image below shows the full 12-tap area of segment 0 (chip_id 2) for an off-axis observation of Ar Lac (obsid 2372). The source is the bright spot to the left of center.
Below are closeups of the source, using the old (version 3) and new (version 4, June 2001) degap maps. In addition to fixing the off-axis problem, the new degap map slightly improves the grating line-spread function and dispersion linearity in the standard spectroscopy region. Recalibration of the LSF and dispersion relation is underway, as is a further fine-tuning of the degap map.
| Old degap | New degap |
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Last modified: 06/14/02
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